sam9x5: MTD numbering changed

sam9x5: MTD numbering changed

[Richard Genoud]

Hi,

I've got an at91sam9g35-cm based board, with 4 partition on the spi-
dataflas and 5 partitions on the NAND flash.
Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND bindings"),
the NAND partitions were mtd0-4 and spi-dataflash partitions mtd5-8.

Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND bindings"),
the spi-dataflash partitions are discovered before the NAND partitions.
So NAND partition became mtd4-8 and spi-dataflash partition mtd0-3.

This broke some script that relied on the mtd numbering.

Updating those scripts to rely on the mtd device name instead of
number is not really a problem. The real problem is when an older
script using mtd numbering is run on the new system : I expect dead
kittens everywhere !

So, I'd like to know if there's a way to force the older numbering ?
(I tried poking around the DTS without succès).

any idea ?

regards,
Richard.


PS:
DTS looks like that:
/dts-v1/;
#include "at91sam9g35.dtsi"
#include "at91sam9x5cm.dtsi"

/ {
	ahb {
		apb {
			spi0: spi@f0000000 {
				pinctrl-0 = <&pinctrl_spi0 &pinctrl_spi0_cs>;
				status = "okay";
				cs-gpios = <&pioA 14 GPIO_ACTIVE_HIGH>, <0>, <0>, <0>;
				m25p80@0 {
					#address-cells = <1>;
					#size-cells = <1>;
					compatible = "atmel,at25df321a";
					spi-max-frequency = <50000000>;
					m25p,fast-read;
					reg = <0>;

					partitions {
						compatible = "fixed-partitions";
						#address-cells = <1>;
						#size-cells = <1>;

						bootpri@0000000 {
							label = "bootpri";
							reg = <0x00000000 0x00008000>;
						};

						bootsec@0008000 {
							label = "bootsec";
							reg = <0x00008000 0x00100000>;
						};

						bootenv@00108000 {
							label = "bootenv";
							reg = <0x00108000 0x00110000>;
						};

						free@00110000 {
							label = "free";
							reg = <0x00110000 0x002f0000>;
						};
					};
				};
			};
		};

                ebi: ebi@10000000 {
                        nand_controller: nand-controller {
                                nand@3 {
                                        status = "okay";
                                        nand-ecc-strength = <4>;
                                };
                        };
                };
	};
};
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Re: sam9x5: MTD numbering changed

[Richard Genoud]

Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :
> +Nicolas
> 
> Hi Richard,
> 
> On Thu, 02 Nov 2017 12:17:16 +0100
> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> 
> > Hi,
> > 
> > I've got an at91sam9g35-cm based board, with 4 partition on the
> > spi-
> > dataflas and 5 partitions on the NAND flash.
> > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND
> > bindings"),
> > the NAND partitions were mtd0-4 and spi-dataflash partitions mtd5-
> > 8.
> > 
> > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND
> > bindings"),
> > the spi-dataflash partitions are discovered before the NAND
> > partitions.
> > So NAND partition became mtd4-8 and spi-dataflash partition mtd0-3.
> > 
> > This broke some script that relied on the mtd numbering.
> > 
> > Updating those scripts to rely on the mtd device name instead of
> > number is not really a problem. The real problem is when an older
> > script using mtd numbering is run on the new system : I expect dead
> > kittens everywhere !
> 
> Crap! That was one of the thing I was afraid of when changing the
> binding: probe order has an impact on ids assigned to MTD devs, and
> since things are not defined at the same place in the DT, it changes
> the probe order.
> 
> > 
> > So, I'd like to know if there's a way to force the older numbering
> > ?
> 
> Reverting the patches is probably the easiest way (and it's easily
> backportable). Now, if we want to switch to the new bindings at some
> point we'll need to support DT aliases for mtd devs:
> 
> aliases {
> 	mtdX = &flashpartN;
> 	mtdY = &flashdevM;
> };
> 
> The problem with this solution is that it only works if all
> partitions
> are defined in the DT, which is not always the case (they can be
> defined
> on the command line with mtdparts=).
Yes, and if they are different from the ones declared in
at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since AFAIK,
we can't remove a declared partitionning.

I'll disable the ebi and switch back to the old binding in my dts for
now.
> 
> > (I tried poking around the DTS without succès).
> > 
> > any idea ?
> 
> I don't have a perfect solution, but the problem you report clearly
> shows that relying on MTD numbering is unsafe and should be avoided.
Clearly, but who doesn't ? ;)


Thanks !

Richard.
> 
> Regards,
> 
> Boris
> 
> > 
> > regards,
> > Richard.

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Re: sam9x5: MTD numbering changed

[Boris Brezillon]

On Thu, 02 Nov 2017 15:13:47 +0100
Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :
> > +Nicolas
> > 
> > Hi Richard,
> > 
> > On Thu, 02 Nov 2017 12:17:16 +0100
> > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >   
> > > Hi,
> > > 
> > > I've got an at91sam9g35-cm based board, with 4 partition on the
> > > spi-
> > > dataflas and 5 partitions on the NAND flash.
> > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND
> > > bindings"),
> > > the NAND partitions were mtd0-4 and spi-dataflash partitions mtd5-
> > > 8.
> > > 
> > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND
> > > bindings"),
> > > the spi-dataflash partitions are discovered before the NAND
> > > partitions.
> > > So NAND partition became mtd4-8 and spi-dataflash partition mtd0-3.
> > > 
> > > This broke some script that relied on the mtd numbering.
> > > 
> > > Updating those scripts to rely on the mtd device name instead of
> > > number is not really a problem. The real problem is when an older
> > > script using mtd numbering is run on the new system : I expect dead
> > > kittens everywhere !  
> > 
> > Crap! That was one of the thing I was afraid of when changing the
> > binding: probe order has an impact on ids assigned to MTD devs, and
> > since things are not defined at the same place in the DT, it changes
> > the probe order.
> >   
> > > 
> > > So, I'd like to know if there's a way to force the older numbering
> > > ?  
> > 
> > Reverting the patches is probably the easiest way (and it's easily
> > backportable). Now, if we want to switch to the new bindings at some
> > point we'll need to support DT aliases for mtd devs:
> > 
> > aliases {
> > 	mtdX = &flashpartN;
> > 	mtdY = &flashdevM;
> > };
> > 
> > The problem with this solution is that it only works if all
> > partitions
> > are defined in the DT, which is not always the case (they can be
> > defined
> > on the command line with mtdparts=).  
> Yes, and if they are different from the ones declared in
> at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since AFAIK,
> we can't remove a declared partitionning.
> 
> I'll disable the ebi and switch back to the old binding in my dts for
> now.

There's another trick you can try: move the node definition around to
try to make the ECC and NAND controller drivers probe before the SPI
one.

It's ugly as hell, but should allow you to keep the new binding.
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Re: sam9x5: MTD numbering changed

[Boris Brezillon]

On Thu, 02 Nov 2017 15:13:47 +0100
Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :
> > +Nicolas
> > 
> > Hi Richard,
> > 
> > On Thu, 02 Nov 2017 12:17:16 +0100
> > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >   
> > > Hi,
> > > 
> > > I've got an at91sam9g35-cm based board, with 4 partition on the
> > > spi-
> > > dataflas and 5 partitions on the NAND flash.
> > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND
> > > bindings"),
> > > the NAND partitions were mtd0-4 and spi-dataflash partitions mtd5-
> > > 8.
> > > 
> > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new NAND
> > > bindings"),
> > > the spi-dataflash partitions are discovered before the NAND
> > > partitions.
> > > So NAND partition became mtd4-8 and spi-dataflash partition mtd0-3.
> > > 
> > > This broke some script that relied on the mtd numbering.
> > > 
> > > Updating those scripts to rely on the mtd device name instead of
> > > number is not really a problem. The real problem is when an older
> > > script using mtd numbering is run on the new system : I expect dead
> > > kittens everywhere !  
> > 
> > Crap! That was one of the thing I was afraid of when changing the
> > binding: probe order has an impact on ids assigned to MTD devs, and
> > since things are not defined at the same place in the DT, it changes
> > the probe order.
> >   
> > > 
> > > So, I'd like to know if there's a way to force the older numbering
> > > ?  
> > 
> > Reverting the patches is probably the easiest way (and it's easily
> > backportable). Now, if we want to switch to the new bindings at some
> > point we'll need to support DT aliases for mtd devs:
> > 
> > aliases {
> > 	mtdX = &flashpartN;
> > 	mtdY = &flashdevM;
> > };
> > 
> > The problem with this solution is that it only works if all
> > partitions
> > are defined in the DT, which is not always the case (they can be
> > defined
> > on the command line with mtdparts=).  
> Yes, and if they are different from the ones declared in
> at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since AFAIK,
> we can't remove a declared partitionning.
> 
> I'll disable the ebi and switch back to the old binding in my dts for
> now.
> >   
> > > (I tried poking around the DTS without succès).
> > > 
> > > any idea ?  
> > 
> > I don't have a perfect solution, but the problem you report clearly
> > shows that relying on MTD numbering is unsafe and should be avoided.  
> Clearly, but who doesn't ? ;)
> 

Just had a lengthy discussion with Alexandre, and he brought a valid
point: there has never been any guarantee on MTD numbering. Not only
the order of DT nodes have an impact on the probe order, but also the
order in which drivers are linked when creating the kernel image. Yes
these things usually don't change, but I'm not sure it's a good idea
to let user-space apps think it will never change in the future.

How about fixing the scripts you were referring to instead of reverting
the change? What's the blocking point?

Regards,

Boris
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Re: sam9x5: MTD numbering changed

[Richard Genoud]

+Nicolas
[its email got lost somehow]
Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a écrit :
> On Thu, 02 Nov 2017 15:13:47 +0100
> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> 
> > Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :
> > > +Nicolas
> > > 
> > > Hi Richard,
> > > 
> > > On Thu, 02 Nov 2017 12:17:16 +0100
> > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > >   
> > > > Hi,
> > > > 
> > > > I've got an at91sam9g35-cm based board, with 4 partition on the
> > > > spi-
> > > > dataflas and 5 partitions on the NAND flash.
> > > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> > > > NAND
> > > > bindings"),
> > > > the NAND partitions were mtd0-4 and spi-dataflash partitions
> > > > mtd5-
> > > > 8.
> > > > 
> > > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> > > > NAND
> > > > bindings"),
> > > > the spi-dataflash partitions are discovered before the NAND
> > > > partitions.
> > > > So NAND partition became mtd4-8 and spi-dataflash partition
> > > > mtd0-3.
> > > > 
> > > > This broke some script that relied on the mtd numbering.
> > > > 
> > > > Updating those scripts to rely on the mtd device name instead
> > > > of
> > > > number is not really a problem. The real problem is when an
> > > > older
> > > > script using mtd numbering is run on the new system : I expect
> > > > dead
> > > > kittens everywhere !  
> > > 
> > > Crap! That was one of the thing I was afraid of when changing the
> > > binding: probe order has an impact on ids assigned to MTD devs,
> > > and
> > > since things are not defined at the same place in the DT, it
> > > changes
> > > the probe order.
> > >   
> > > > 
> > > > So, I'd like to know if there's a way to force the older
> > > > numbering
> > > > ?  
> > > 
> > > Reverting the patches is probably the easiest way (and it's
> > > easily
> > > backportable). Now, if we want to switch to the new bindings at
> > > some
> > > point we'll need to support DT aliases for mtd devs:
> > > 
> > > aliases {
> > > 	mtdX = &flashpartN;
> > > 	mtdY = &flashdevM;
> > > };
> > > 
> > > The problem with this solution is that it only works if all
> > > partitions
> > > are defined in the DT, which is not always the case (they can be
> > > defined
> > > on the command line with mtdparts=).  
> > 
> > Yes, and if they are different from the ones declared in
> > at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since
> > AFAIK,
> > we can't remove a declared partitionning.
> > 
> > I'll disable the ebi and switch back to the old binding in my dts
> > for
> > now.
> > >   
> > > > (I tried poking around the DTS without succès).
> > > > 
> > > > any idea ?  
> > > 
> > > I don't have a perfect solution, but the problem you report
> > > clearly
> > > shows that relying on MTD numbering is unsafe and should be
> > > avoided.  
> > 
> > Clearly, but who doesn't ? ;)
> > 
> 
> Just had a lengthy discussion with Alexandre, and he brought a valid
> point: there has never been any guarantee on MTD numbering. Not only
> the order of DT nodes have an impact on the probe order, but also the
> order in which drivers are linked when creating the kernel image. Yes
> these things usually don't change, but I'm not sure it's a good idea
> to let user-space apps think it will never change in the future.
> 
> How about fixing the scripts you were referring to instead of
> reverting
> the change? What's the blocking point?

I already fixed the user-space scripts (and actually, they predate the
device-tree era, so at that time, relying on MTD numbering wasn't so
bad :)).
Anyway, here's the blocking point :

We have firmwares with an embedded script to update our boards. (more
or less a FW + script in a zip file).
Those old firmwares are already in the wild and rely on the old MTD
numbering (yes, that's bad).


So, even if all new scripts are corrected in the new firmwares,
downgrading a board with an old firmware/old script will brick the
board.
So I'll have to detect that and forbid downgrading.

That's not the end of the world, but if I can find a trick to prevent
it, I'll be happier !


Regards,

Richard


> 
> Regards,
> 
> Boris
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Re: sam9x5: MTD numbering changed

[Boris Brezillon]

On Thu, 02 Nov 2017 16:28:13 +0100
Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> +Nicolas
> [its email got lost somehow]
> Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a écrit :
> > On Thu, 02 Nov 2017 15:13:47 +0100
> > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >   
> > > Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :  
> > > > +Nicolas
> > > > 
> > > > Hi Richard,
> > > > 
> > > > On Thu, 02 Nov 2017 12:17:16 +0100
> > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > >     
> > > > > Hi,
> > > > > 
> > > > > I've got an at91sam9g35-cm based board, with 4 partition on the
> > > > > spi-
> > > > > dataflas and 5 partitions on the NAND flash.
> > > > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> > > > > NAND
> > > > > bindings"),
> > > > > the NAND partitions were mtd0-4 and spi-dataflash partitions
> > > > > mtd5-
> > > > > 8.
> > > > > 
> > > > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> > > > > NAND
> > > > > bindings"),
> > > > > the spi-dataflash partitions are discovered before the NAND
> > > > > partitions.
> > > > > So NAND partition became mtd4-8 and spi-dataflash partition
> > > > > mtd0-3.
> > > > > 
> > > > > This broke some script that relied on the mtd numbering.
> > > > > 
> > > > > Updating those scripts to rely on the mtd device name instead
> > > > > of
> > > > > number is not really a problem. The real problem is when an
> > > > > older
> > > > > script using mtd numbering is run on the new system : I expect
> > > > > dead
> > > > > kittens everywhere !    
> > > > 
> > > > Crap! That was one of the thing I was afraid of when changing the
> > > > binding: probe order has an impact on ids assigned to MTD devs,
> > > > and
> > > > since things are not defined at the same place in the DT, it
> > > > changes
> > > > the probe order.
> > > >     
> > > > > 
> > > > > So, I'd like to know if there's a way to force the older
> > > > > numbering
> > > > > ?    
> > > > 
> > > > Reverting the patches is probably the easiest way (and it's
> > > > easily
> > > > backportable). Now, if we want to switch to the new bindings at
> > > > some
> > > > point we'll need to support DT aliases for mtd devs:
> > > > 
> > > > aliases {
> > > > 	mtdX = &flashpartN;
> > > > 	mtdY = &flashdevM;
> > > > };
> > > > 
> > > > The problem with this solution is that it only works if all
> > > > partitions
> > > > are defined in the DT, which is not always the case (they can be
> > > > defined
> > > > on the command line with mtdparts=).    
> > > 
> > > Yes, and if they are different from the ones declared in
> > > at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since
> > > AFAIK,
> > > we can't remove a declared partitionning.
> > > 
> > > I'll disable the ebi and switch back to the old binding in my dts
> > > for
> > > now.  
> > > >     
> > > > > (I tried poking around the DTS without succès).
> > > > > 
> > > > > any idea ?    
> > > > 
> > > > I don't have a perfect solution, but the problem you report
> > > > clearly
> > > > shows that relying on MTD numbering is unsafe and should be
> > > > avoided.    
> > > 
> > > Clearly, but who doesn't ? ;)
> > >   
> > 
> > Just had a lengthy discussion with Alexandre, and he brought a valid
> > point: there has never been any guarantee on MTD numbering. Not only
> > the order of DT nodes have an impact on the probe order, but also the
> > order in which drivers are linked when creating the kernel image. Yes
> > these things usually don't change, but I'm not sure it's a good idea
> > to let user-space apps think it will never change in the future.
> > 
> > How about fixing the scripts you were referring to instead of
> > reverting
> > the change? What's the blocking point?  
> 
> I already fixed the user-space scripts (and actually, they predate the
> device-tree era, so at that time, relying on MTD numbering wasn't so
> bad :)).
> Anyway, here's the blocking point :
> 
> We have firmwares with an embedded script to update our boards. (more
> or less a FW + script in a zip file).
> Those old firmwares are already in the wild and rely on the old MTD
> numbering (yes, that's bad).
> 
> 
> So, even if all new scripts are corrected in the new firmwares,
> downgrading a board with an old firmware/old script will brick the
> board.
> So I'll have to detect that and forbid downgrading.

Not sure what you refer to when you're talking about 'FW', but I'd
expect it to contain a kernel [+ a dtb] + a rootfs, so if you're using
an old "FW+update-script", you will still have the old numbering and
the old script will work just fine, and if you switch to a newer version
of the "FW+update-script" based on a 4.13 kernel+dtb you will anyway
have the updated script. Am I missing something?

> 
> That's not the end of the world, but if I can find a trick to prevent
> it, I'll be happier !
> 
> 
> Regards,
> 
> Richard
> 
> 
> > 
> > Regards,
> > 
> > Boris  
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

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Re: sam9x5: MTD numbering changed

[Richard Genoud]

2017-11-02 16:45 GMT+01:00 Boris Brezillon <boris.brezillon@free-electrons.com>:
> On Thu, 02 Nov 2017 16:28:13 +0100
> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>> +Nicolas
>> [its email got lost somehow]
>> Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a écrit :
>> > On Thu, 02 Nov 2017 15:13:47 +0100
>> > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> >
>> > > Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :
>> > > > +Nicolas
>> > > >
>> > > > Hi Richard,
>> > > >
>> > > > On Thu, 02 Nov 2017 12:17:16 +0100
>> > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> > > >
>> > > > > Hi,
>> > > > >
>> > > > > I've got an at91sam9g35-cm based board, with 4 partition on the
>> > > > > spi-
>> > > > > dataflas and 5 partitions on the NAND flash.
>> > > > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
>> > > > > NAND
>> > > > > bindings"),
>> > > > > the NAND partitions were mtd0-4 and spi-dataflash partitions
>> > > > > mtd5-
>> > > > > 8.
>> > > > >
>> > > > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
>> > > > > NAND
>> > > > > bindings"),
>> > > > > the spi-dataflash partitions are discovered before the NAND
>> > > > > partitions.
>> > > > > So NAND partition became mtd4-8 and spi-dataflash partition
>> > > > > mtd0-3.
>> > > > >
>> > > > > This broke some script that relied on the mtd numbering.
>> > > > >
>> > > > > Updating those scripts to rely on the mtd device name instead
>> > > > > of
>> > > > > number is not really a problem. The real problem is when an
>> > > > > older
>> > > > > script using mtd numbering is run on the new system : I expect
>> > > > > dead
>> > > > > kittens everywhere !
>> > > >
>> > > > Crap! That was one of the thing I was afraid of when changing the
>> > > > binding: probe order has an impact on ids assigned to MTD devs,
>> > > > and
>> > > > since things are not defined at the same place in the DT, it
>> > > > changes
>> > > > the probe order.
>> > > >
>> > > > >
>> > > > > So, I'd like to know if there's a way to force the older
>> > > > > numbering
>> > > > > ?
>> > > >
>> > > > Reverting the patches is probably the easiest way (and it's
>> > > > easily
>> > > > backportable). Now, if we want to switch to the new bindings at
>> > > > some
>> > > > point we'll need to support DT aliases for mtd devs:
>> > > >
>> > > > aliases {
>> > > >         mtdX = &flashpartN;
>> > > >         mtdY = &flashdevM;
>> > > > };
>> > > >
>> > > > The problem with this solution is that it only works if all
>> > > > partitions
>> > > > are defined in the DT, which is not always the case (they can be
>> > > > defined
>> > > > on the command line with mtdparts=).
>> > >
>> > > Yes, and if they are different from the ones declared in
>> > > at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since
>> > > AFAIK,
>> > > we can't remove a declared partitionning.
>> > >
>> > > I'll disable the ebi and switch back to the old binding in my dts
>> > > for
>> > > now.
>> > > >
>> > > > > (I tried poking around the DTS without succès).
>> > > > >
>> > > > > any idea ?
>> > > >
>> > > > I don't have a perfect solution, but the problem you report
>> > > > clearly
>> > > > shows that relying on MTD numbering is unsafe and should be
>> > > > avoided.
>> > >
>> > > Clearly, but who doesn't ? ;)
>> > >
>> >
>> > Just had a lengthy discussion with Alexandre, and he brought a valid
>> > point: there has never been any guarantee on MTD numbering. Not only
>> > the order of DT nodes have an impact on the probe order, but also the
>> > order in which drivers are linked when creating the kernel image. Yes
>> > these things usually don't change, but I'm not sure it's a good idea
>> > to let user-space apps think it will never change in the future.
>> >
>> > How about fixing the scripts you were referring to instead of
>> > reverting
>> > the change? What's the blocking point?
>>
>> I already fixed the user-space scripts (and actually, they predate the
>> device-tree era, so at that time, relying on MTD numbering wasn't so
>> bad :)).
>> Anyway, here's the blocking point :
>>
>> We have firmwares with an embedded script to update our boards. (more
>> or less a FW + script in a zip file).
>> Those old firmwares are already in the wild and rely on the old MTD
>> numbering (yes, that's bad).
>>
>>
>> So, even if all new scripts are corrected in the new firmwares,
>> downgrading a board with an old firmware/old script will brick the
>> board.
>> So I'll have to detect that and forbid downgrading.
>
> Not sure what you refer to when you're talking about 'FW', but I'd
> expect it to contain a kernel [+ a dtb] + a rootfs, so if you're using
> an old "FW+update-script", you will still have the old numbering and
> the old script will work just fine, and if you switch to a newer version
> of the "FW+update-script" based on a 4.13 kernel+dtb you will anyway
> have the updated script. Am I missing something?

Ok, let's have an example.
New firmware : kernel
4.14+dtb+rootfs+uboot+uboot_env+at91bootstrap+new update script.
Old firmware : kernel 4.11 + dtb + rootfs + uboot +
uboot_env+at91bootstrap+old update script.

Let's suppose there's the new firmware on the board (let's call it
4.14 firmware) :
MTD0 is the dataflash partition 0 (at91bootstrap)
MTD1 is the dataflash part1 (uboot)
MTD2 is the dataflash part2 (ubootenv)
MTD3 is the dataflash part3 (free space)
MTD4 is the NAND part 0 (dtb)
MTD5 is the NAND part 1 (kernel)
MTD6 is the NAND part 2 (UBI) <- in this one, there're 3 ubifs volumes
: rootfs/rootfs2/data

The thing is, the update script runs in user-space and updates the
kernel, dtb, uboot, bootstrap and flashes the rootfs2.
(on next boot, the rootfs2/rootfs will be atomically swapped)
So, when downgrading, the old update script is executed on the board,
under the 4.14 firmware, thinking that MTD0 is the NAND part0 (dtb),
while it is actually the dataflash part0 (bootstrap).
=> the bootstrap is erased and replaced by the dtb (well, actually, it
won't even be like that since there will be a mismatch between
nandwrite/flash_part).

It's not a huge big deal since I have another way to flash all
partitions from uboot, but this can't be done remotely.


>
>>
>> That's not the end of the world, but if I can find a trick to prevent
>> it, I'll be happier !
>>
>>
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Re: sam9x5: MTD numbering changed

[Boris Brezillon]

On Thu, 2 Nov 2017 18:36:35 +0100
Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> 2017-11-02 16:45 GMT+01:00 Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>:
> > On Thu, 02 Nov 2017 16:28:13 +0100
> > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >  
> >> +Nicolas
> >> [its email got lost somehow]
> >> Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a écrit :  
> >> > On Thu, 02 Nov 2017 15:13:47 +0100
> >> > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >> >  
> >> > > Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :  
> >> > > > +Nicolas
> >> > > >
> >> > > > Hi Richard,
> >> > > >
> >> > > > On Thu, 02 Nov 2017 12:17:16 +0100
> >> > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >> > > >  
> >> > > > > Hi,
> >> > > > >
> >> > > > > I've got an at91sam9g35-cm based board, with 4 partition on the
> >> > > > > spi-
> >> > > > > dataflas and 5 partitions on the NAND flash.
> >> > > > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> >> > > > > NAND
> >> > > > > bindings"),
> >> > > > > the NAND partitions were mtd0-4 and spi-dataflash partitions
> >> > > > > mtd5-
> >> > > > > 8.
> >> > > > >
> >> > > > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> >> > > > > NAND
> >> > > > > bindings"),
> >> > > > > the spi-dataflash partitions are discovered before the NAND
> >> > > > > partitions.
> >> > > > > So NAND partition became mtd4-8 and spi-dataflash partition
> >> > > > > mtd0-3.
> >> > > > >
> >> > > > > This broke some script that relied on the mtd numbering.
> >> > > > >
> >> > > > > Updating those scripts to rely on the mtd device name instead
> >> > > > > of
> >> > > > > number is not really a problem. The real problem is when an
> >> > > > > older
> >> > > > > script using mtd numbering is run on the new system : I expect
> >> > > > > dead
> >> > > > > kittens everywhere !  
> >> > > >
> >> > > > Crap! That was one of the thing I was afraid of when changing the
> >> > > > binding: probe order has an impact on ids assigned to MTD devs,
> >> > > > and
> >> > > > since things are not defined at the same place in the DT, it
> >> > > > changes
> >> > > > the probe order.
> >> > > >  
> >> > > > >
> >> > > > > So, I'd like to know if there's a way to force the older
> >> > > > > numbering
> >> > > > > ?  
> >> > > >
> >> > > > Reverting the patches is probably the easiest way (and it's
> >> > > > easily
> >> > > > backportable). Now, if we want to switch to the new bindings at
> >> > > > some
> >> > > > point we'll need to support DT aliases for mtd devs:
> >> > > >
> >> > > > aliases {
> >> > > >         mtdX = &flashpartN;
> >> > > >         mtdY = &flashdevM;
> >> > > > };
> >> > > >
> >> > > > The problem with this solution is that it only works if all
> >> > > > partitions
> >> > > > are defined in the DT, which is not always the case (they can be
> >> > > > defined
> >> > > > on the command line with mtdparts=).  
> >> > >
> >> > > Yes, and if they are different from the ones declared in
> >> > > at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since
> >> > > AFAIK,
> >> > > we can't remove a declared partitionning.
> >> > >
> >> > > I'll disable the ebi and switch back to the old binding in my dts
> >> > > for
> >> > > now.  
> >> > > >  
> >> > > > > (I tried poking around the DTS without succès).
> >> > > > >
> >> > > > > any idea ?  
> >> > > >
> >> > > > I don't have a perfect solution, but the problem you report
> >> > > > clearly
> >> > > > shows that relying on MTD numbering is unsafe and should be
> >> > > > avoided.  
> >> > >
> >> > > Clearly, but who doesn't ? ;)
> >> > >  
> >> >
> >> > Just had a lengthy discussion with Alexandre, and he brought a valid
> >> > point: there has never been any guarantee on MTD numbering. Not only
> >> > the order of DT nodes have an impact on the probe order, but also the
> >> > order in which drivers are linked when creating the kernel image. Yes
> >> > these things usually don't change, but I'm not sure it's a good idea
> >> > to let user-space apps think it will never change in the future.
> >> >
> >> > How about fixing the scripts you were referring to instead of
> >> > reverting
> >> > the change? What's the blocking point?  
> >>
> >> I already fixed the user-space scripts (and actually, they predate the
> >> device-tree era, so at that time, relying on MTD numbering wasn't so
> >> bad :)).
> >> Anyway, here's the blocking point :
> >>
> >> We have firmwares with an embedded script to update our boards. (more
> >> or less a FW + script in a zip file).
> >> Those old firmwares are already in the wild and rely on the old MTD
> >> numbering (yes, that's bad).
> >>
> >>
> >> So, even if all new scripts are corrected in the new firmwares,
> >> downgrading a board with an old firmware/old script will brick the
> >> board.
> >> So I'll have to detect that and forbid downgrading.  
> >
> > Not sure what you refer to when you're talking about 'FW', but I'd
> > expect it to contain a kernel [+ a dtb] + a rootfs, so if you're using
> > an old "FW+update-script", you will still have the old numbering and
> > the old script will work just fine, and if you switch to a newer version
> > of the "FW+update-script" based on a 4.13 kernel+dtb you will anyway
> > have the updated script. Am I missing something?  
> 
> Ok, let's have an example.
> New firmware : kernel
> 4.14+dtb+rootfs+uboot+uboot_env+at91bootstrap+new update script.
> Old firmware : kernel 4.11 + dtb + rootfs + uboot +
> uboot_env+at91bootstrap+old update script.
> 
> Let's suppose there's the new firmware on the board (let's call it
> 4.14 firmware) :
> MTD0 is the dataflash partition 0 (at91bootstrap)
> MTD1 is the dataflash part1 (uboot)
> MTD2 is the dataflash part2 (ubootenv)
> MTD3 is the dataflash part3 (free space)
> MTD4 is the NAND part 0 (dtb)
> MTD5 is the NAND part 1 (kernel)
> MTD6 is the NAND part 2 (UBI) <- in this one, there're 3 ubifs volumes
> : rootfs/rootfs2/data
> 
> The thing is, the update script runs in user-space and updates the
> kernel, dtb, uboot, bootstrap and flashes the rootfs2.
> (on next boot, the rootfs2/rootfs will be atomically swapped)
> So, when downgrading, the old update script is executed on the board,
> under the 4.14 firmware, thinking that MTD0 is the NAND part0 (dtb),
> while it is actually the dataflash part0 (bootstrap).
> => the bootstrap is erased and replaced by the dtb (well, actually, it  
> won't even be like that since there will be a mismatch between
> nandwrite/flash_part).

Can you re-generate zip archives for old versions? If you can maybe it
would be simpler to just embed the new update script (assuming this
script works fine with both old and new FW) in old FW archives.

> 
> It's not a huge big deal since I have another way to flash all
> partitions from uboot, but this can't be done remotely.
> 
> 
> >  
> >>
> >> That's not the end of the world, but if I can find a trick to prevent
> >> it, I'll be happier !
> >>
> >>  

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Re: sam9x5: MTD numbering changed

[Cyrille Pitchen]

Hi all,

Le 02/11/2017 à 18:58, Boris Brezillon a écrit :
> On Thu, 2 Nov 2017 18:36:35 +0100
> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> 
>> 2017-11-02 16:45 GMT+01:00 Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>:
>>> On Thu, 02 Nov 2017 16:28:13 +0100
>>> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>>  
>>>> +Nicolas
>>>> [its email got lost somehow]
>>>> Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a écrit :  
>>>>> On Thu, 02 Nov 2017 15:13:47 +0100
>>>>> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>>>>  
>>>>>> Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :  
>>>>>>> +Nicolas
>>>>>>>
>>>>>>> Hi Richard,
>>>>>>>
>>>>>>> On Thu, 02 Nov 2017 12:17:16 +0100
>>>>>>> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>>>>>>  
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I've got an at91sam9g35-cm based board, with 4 partition on the
>>>>>>>> spi-
>>>>>>>> dataflas and 5 partitions on the NAND flash.
>>>>>>>> Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
>>>>>>>> NAND
>>>>>>>> bindings"),
>>>>>>>> the NAND partitions were mtd0-4 and spi-dataflash partitions
>>>>>>>> mtd5-
>>>>>>>> 8.
>>>>>>>>
>>>>>>>> Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
>>>>>>>> NAND
>>>>>>>> bindings"),
>>>>>>>> the spi-dataflash partitions are discovered before the NAND
>>>>>>>> partitions.
>>>>>>>> So NAND partition became mtd4-8 and spi-dataflash partition
>>>>>>>> mtd0-3.
>>>>>>>>
>>>>>>>> This broke some script that relied on the mtd numbering.
>>>>>>>>
>>>>>>>> Updating those scripts to rely on the mtd device name instead
>>>>>>>> of
>>>>>>>> number is not really a problem. The real problem is when an
>>>>>>>> older
>>>>>>>> script using mtd numbering is run on the new system : I expect
>>>>>>>> dead
>>>>>>>> kittens everywhere !  
>>>>>>>
>>>>>>> Crap! That was one of the thing I was afraid of when changing the
>>>>>>> binding: probe order has an impact on ids assigned to MTD devs,
>>>>>>> and
>>>>>>> since things are not defined at the same place in the DT, it
>>>>>>> changes
>>>>>>> the probe order.
>>>>>>>  
>>>>>>>>
>>>>>>>> So, I'd like to know if there's a way to force the older
>>>>>>>> numbering
>>>>>>>> ?  
>>>>>>>
>>>>>>> Reverting the patches is probably the easiest way (and it's
>>>>>>> easily
>>>>>>> backportable). Now, if we want to switch to the new bindings at
>>>>>>> some
>>>>>>> point we'll need to support DT aliases for mtd devs:
>>>>>>>
>>>>>>> aliases {
>>>>>>>         mtdX = &flashpartN;
>>>>>>>         mtdY = &flashdevM;
>>>>>>> };
>>>>>>>
>>>>>>> The problem with this solution is that it only works if all
>>>>>>> partitions
>>>>>>> are defined in the DT, which is not always the case (they can be
>>>>>>> defined
>>>>>>> on the command line with mtdparts=).  
>>>>>>
>>>>>> Yes, and if they are different from the ones declared in
>>>>>> at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since
>>>>>> AFAIK,
>>>>>> we can't remove a declared partitionning.
>>>>>>
>>>>>> I'll disable the ebi and switch back to the old binding in my dts
>>>>>> for
>>>>>> now.  
>>>>>>>  
>>>>>>>> (I tried poking around the DTS without succès).
>>>>>>>>
>>>>>>>> any idea ?  
>>>>>>>
>>>>>>> I don't have a perfect solution, but the problem you report
>>>>>>> clearly
>>>>>>> shows that relying on MTD numbering is unsafe and should be
>>>>>>> avoided.  
>>>>>>
>>>>>> Clearly, but who doesn't ? ;)
>>>>>>  
>>>>>
>>>>> Just had a lengthy discussion with Alexandre, and he brought a valid
>>>>> point: there has never been any guarantee on MTD numbering. Not only
>>>>> the order of DT nodes have an impact on the probe order, but also the
>>>>> order in which drivers are linked when creating the kernel image. Yes
>>>>> these things usually don't change, but I'm not sure it's a good idea
>>>>> to let user-space apps think it will never change in the future.
>>>>>
>>>>> How about fixing the scripts you were referring to instead of
>>>>> reverting
>>>>> the change? What's the blocking point?  
>>>>
>>>> I already fixed the user-space scripts (and actually, they predate the
>>>> device-tree era, so at that time, relying on MTD numbering wasn't so
>>>> bad :)).
>>>> Anyway, here's the blocking point :
>>>>
>>>> We have firmwares with an embedded script to update our boards. (more
>>>> or less a FW + script in a zip file).
>>>> Those old firmwares are already in the wild and rely on the old MTD
>>>> numbering (yes, that's bad).
>>>>
>>>>
>>>> So, even if all new scripts are corrected in the new firmwares,
>>>> downgrading a board with an old firmware/old script will brick the
>>>> board.
>>>> So I'll have to detect that and forbid downgrading.  
>>>
>>> Not sure what you refer to when you're talking about 'FW', but I'd
>>> expect it to contain a kernel [+ a dtb] + a rootfs, so if you're using
>>> an old "FW+update-script", you will still have the old numbering and
>>> the old script will work just fine, and if you switch to a newer version
>>> of the "FW+update-script" based on a 4.13 kernel+dtb you will anyway
>>> have the updated script. Am I missing something?  
>>
>> Ok, let's have an example.
>> New firmware : kernel
>> 4.14+dtb+rootfs+uboot+uboot_env+at91bootstrap+new update script.
>> Old firmware : kernel 4.11 + dtb + rootfs + uboot +
>> uboot_env+at91bootstrap+old update script.
>>
>> Let's suppose there's the new firmware on the board (let's call it
>> 4.14 firmware) :
>> MTD0 is the dataflash partition 0 (at91bootstrap)
>> MTD1 is the dataflash part1 (uboot)
>> MTD2 is the dataflash part2 (ubootenv)
>> MTD3 is the dataflash part3 (free space)
>> MTD4 is the NAND part 0 (dtb)
>> MTD5 is the NAND part 1 (kernel)
>> MTD6 is the NAND part 2 (UBI) <- in this one, there're 3 ubifs volumes
>> : rootfs/rootfs2/data
>>
>> The thing is, the update script runs in user-space and updates the
>> kernel, dtb, uboot, bootstrap and flashes the rootfs2.
>> (on next boot, the rootfs2/rootfs will be atomically swapped)
>> So, when downgrading, the old update script is executed on the board,
>> under the 4.14 firmware, thinking that MTD0 is the NAND part0 (dtb),
>> while it is actually the dataflash part0 (bootstrap).
>> => the bootstrap is erased and replaced by the dtb (well, actually, it  
>> won't even be like that since there will be a mismatch between
>> nandwrite/flash_part).
> 
> Can you re-generate zip archives for old versions? If you can maybe it
> would be simpler to just embed the new update script (assuming this
> script works fine with both old and new FW) in old FW archives.
>

No sure, I've totally understand the issue, if not sorry for the noise!

Would it be possible to use some udev rules to create some symbolic links
in /dev based on ATTRS{name}, the mtd partition names?

something like:
/dev/mtd-at91bootstrap -> /dev/mtd0
/dev/mtd-uboot -> /dev/mtd1
/dev/mtd-ubootenv -> /dev/mtd2
/dev/mtd-free -> /dev/mtd3
/dev/mtd-dtb -> /dev/mtd4
/dev/mtd-kernel -> /dev/mtd5
/dev/mtd-ubi -> /dev/mtd6

Then if the new update script only uses symbolic names, it should work with
both linux 4.11 and 4.14 kernels.

But I think I didn't totally understand why/how the old update script would
be run under the new kernel :p

Best regards,

Cyrille
 
>>
>> It's not a huge big deal since I have another way to flash all
>> partitions from uboot, but this can't be done remotely.
>>
>>
>>>  
>>>>
>>>> That's not the end of the world, but if I can find a trick to prevent
>>>> it, I'll be happier !
>>>>
>>>>  
> 
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
> 

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Re: sam9x5: MTD numbering changed

[Boris Brezillon]

On Fri, 3 Nov 2017 00:12:17 +0100
Cyrille Pitchen <cyrille.pitchen-yU5RGvR974pGWvitb5QawA@public.gmane.org> wrote:

> Hi all,
> 
> Le 02/11/2017 à 18:58, Boris Brezillon a écrit :
> > On Thu, 2 Nov 2017 18:36:35 +0100
> > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >   
> >> 2017-11-02 16:45 GMT+01:00 Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>:  
> >>> On Thu, 02 Nov 2017 16:28:13 +0100
> >>> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >>>    
> >>>> +Nicolas
> >>>> [its email got lost somehow]
> >>>> Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a écrit :    
> >>>>> On Thu, 02 Nov 2017 15:13:47 +0100
> >>>>> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >>>>>    
> >>>>>> Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a écrit :    
> >>>>>>> +Nicolas
> >>>>>>>
> >>>>>>> Hi Richard,
> >>>>>>>
> >>>>>>> On Thu, 02 Nov 2017 12:17:16 +0100
> >>>>>>> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >>>>>>>    
> >>>>>>>> Hi,
> >>>>>>>>
> >>>>>>>> I've got an at91sam9g35-cm based board, with 4 partition on the
> >>>>>>>> spi-
> >>>>>>>> dataflas and 5 partitions on the NAND flash.
> >>>>>>>> Before commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> >>>>>>>> NAND
> >>>>>>>> bindings"),
> >>>>>>>> the NAND partitions were mtd0-4 and spi-dataflash partitions
> >>>>>>>> mtd5-
> >>>>>>>> 8.
> >>>>>>>>
> >>>>>>>> Since commit 1004a2977bdc ("ARM: dts: at91: Switch to the new
> >>>>>>>> NAND
> >>>>>>>> bindings"),
> >>>>>>>> the spi-dataflash partitions are discovered before the NAND
> >>>>>>>> partitions.
> >>>>>>>> So NAND partition became mtd4-8 and spi-dataflash partition
> >>>>>>>> mtd0-3.
> >>>>>>>>
> >>>>>>>> This broke some script that relied on the mtd numbering.
> >>>>>>>>
> >>>>>>>> Updating those scripts to rely on the mtd device name instead
> >>>>>>>> of
> >>>>>>>> number is not really a problem. The real problem is when an
> >>>>>>>> older
> >>>>>>>> script using mtd numbering is run on the new system : I expect
> >>>>>>>> dead
> >>>>>>>> kittens everywhere !    
> >>>>>>>
> >>>>>>> Crap! That was one of the thing I was afraid of when changing the
> >>>>>>> binding: probe order has an impact on ids assigned to MTD devs,
> >>>>>>> and
> >>>>>>> since things are not defined at the same place in the DT, it
> >>>>>>> changes
> >>>>>>> the probe order.
> >>>>>>>    
> >>>>>>>>
> >>>>>>>> So, I'd like to know if there's a way to force the older
> >>>>>>>> numbering
> >>>>>>>> ?    
> >>>>>>>
> >>>>>>> Reverting the patches is probably the easiest way (and it's
> >>>>>>> easily
> >>>>>>> backportable). Now, if we want to switch to the new bindings at
> >>>>>>> some
> >>>>>>> point we'll need to support DT aliases for mtd devs:
> >>>>>>>
> >>>>>>> aliases {
> >>>>>>>         mtdX = &flashpartN;
> >>>>>>>         mtdY = &flashdevM;
> >>>>>>> };
> >>>>>>>
> >>>>>>> The problem with this solution is that it only works if all
> >>>>>>> partitions
> >>>>>>> are defined in the DT, which is not always the case (they can be
> >>>>>>> defined
> >>>>>>> on the command line with mtdparts=).    
> >>>>>>
> >>>>>> Yes, and if they are different from the ones declared in
> >>>>>> at91sam9x5cm.dtsi, they are likely defined with mtdparts=, since
> >>>>>> AFAIK,
> >>>>>> we can't remove a declared partitionning.
> >>>>>>
> >>>>>> I'll disable the ebi and switch back to the old binding in my dts
> >>>>>> for
> >>>>>> now.    
> >>>>>>>    
> >>>>>>>> (I tried poking around the DTS without succès).
> >>>>>>>>
> >>>>>>>> any idea ?    
> >>>>>>>
> >>>>>>> I don't have a perfect solution, but the problem you report
> >>>>>>> clearly
> >>>>>>> shows that relying on MTD numbering is unsafe and should be
> >>>>>>> avoided.    
> >>>>>>
> >>>>>> Clearly, but who doesn't ? ;)
> >>>>>>    
> >>>>>
> >>>>> Just had a lengthy discussion with Alexandre, and he brought a valid
> >>>>> point: there has never been any guarantee on MTD numbering. Not only
> >>>>> the order of DT nodes have an impact on the probe order, but also the
> >>>>> order in which drivers are linked when creating the kernel image. Yes
> >>>>> these things usually don't change, but I'm not sure it's a good idea
> >>>>> to let user-space apps think it will never change in the future.
> >>>>>
> >>>>> How about fixing the scripts you were referring to instead of
> >>>>> reverting
> >>>>> the change? What's the blocking point?    
> >>>>
> >>>> I already fixed the user-space scripts (and actually, they predate the
> >>>> device-tree era, so at that time, relying on MTD numbering wasn't so
> >>>> bad :)).
> >>>> Anyway, here's the blocking point :
> >>>>
> >>>> We have firmwares with an embedded script to update our boards. (more
> >>>> or less a FW + script in a zip file).
> >>>> Those old firmwares are already in the wild and rely on the old MTD
> >>>> numbering (yes, that's bad).
> >>>>
> >>>>
> >>>> So, even if all new scripts are corrected in the new firmwares,
> >>>> downgrading a board with an old firmware/old script will brick the
> >>>> board.
> >>>> So I'll have to detect that and forbid downgrading.    
> >>>
> >>> Not sure what you refer to when you're talking about 'FW', but I'd
> >>> expect it to contain a kernel [+ a dtb] + a rootfs, so if you're using
> >>> an old "FW+update-script", you will still have the old numbering and
> >>> the old script will work just fine, and if you switch to a newer version
> >>> of the "FW+update-script" based on a 4.13 kernel+dtb you will anyway
> >>> have the updated script. Am I missing something?    
> >>
> >> Ok, let's have an example.
> >> New firmware : kernel
> >> 4.14+dtb+rootfs+uboot+uboot_env+at91bootstrap+new update script.
> >> Old firmware : kernel 4.11 + dtb + rootfs + uboot +
> >> uboot_env+at91bootstrap+old update script.
> >>
> >> Let's suppose there's the new firmware on the board (let's call it
> >> 4.14 firmware) :
> >> MTD0 is the dataflash partition 0 (at91bootstrap)
> >> MTD1 is the dataflash part1 (uboot)
> >> MTD2 is the dataflash part2 (ubootenv)
> >> MTD3 is the dataflash part3 (free space)
> >> MTD4 is the NAND part 0 (dtb)
> >> MTD5 is the NAND part 1 (kernel)
> >> MTD6 is the NAND part 2 (UBI) <- in this one, there're 3 ubifs volumes
> >> : rootfs/rootfs2/data
> >>
> >> The thing is, the update script runs in user-space and updates the
> >> kernel, dtb, uboot, bootstrap and flashes the rootfs2.
> >> (on next boot, the rootfs2/rootfs will be atomically swapped)
> >> So, when downgrading, the old update script is executed on the board,
> >> under the 4.14 firmware, thinking that MTD0 is the NAND part0 (dtb),
> >> while it is actually the dataflash part0 (bootstrap).  
> >> => the bootstrap is erased and replaced by the dtb (well, actually, it    
> >> won't even be like that since there will be a mismatch between
> >> nandwrite/flash_part).  
> > 
> > Can you re-generate zip archives for old versions? If you can maybe it
> > would be simpler to just embed the new update script (assuming this
> > script works fine with both old and new FW) in old FW archives.
> >  
> 
> No sure, I've totally understand the issue, if not sorry for the noise!
> 
> Would it be possible to use some udev rules to create some symbolic links
> in /dev based on ATTRS{name}, the mtd partition names?
> 
> something like:
> /dev/mtd-at91bootstrap -> /dev/mtd0
> /dev/mtd-uboot -> /dev/mtd1
> /dev/mtd-ubootenv -> /dev/mtd2
> /dev/mtd-free -> /dev/mtd3
> /dev/mtd-dtb -> /dev/mtd4
> /dev/mtd-kernel -> /dev/mtd5
> /dev/mtd-ubi -> /dev/mtd6

Yep, we should definitely have a udev rule populating
a /dev/mtd/by-name/ directory, just like there is a /dev/disk/by-uuid.

> 
> Then if the new update script only uses symbolic names, it should work with
> both linux 4.11 and 4.14 kernels.
> 
> But I think I didn't totally understand why/how the old update script would
> be run under the new kernel :p

The problem is that the update script in embedded in the archive
containing image(s) to flash, so old archives still have the old
script, which means, if you try to downgrade to an older version from a
new version you're screwed because it will use /dev/mtdX directly
without checking if this is the right partition.
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Re: sam9x5: MTD numbering changed

[Richard Genoud]

Le vendredi 03 novembre 2017 à 09:06 +0100, Boris Brezillon a écrit :
> On Fri, 3 Nov 2017 00:12:17 +0100
> Cyrille Pitchen <cyrille.pitchen-yU5RGvR974pGWvitb5QawA@public.gmane.org> wrote:
> 
> > Hi all,
> > 
> > Le 02/11/2017 à 18:58, Boris Brezillon a écrit :
> > > On Thu, 2 Nov 2017 18:36:35 +0100
> > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > >   
> > > > 2017-11-02 16:45 GMT+01:00 Boris Brezillon <boris.brezillon@fre
> > > > e-electrons.com>:  
> > > > > On Thu, 02 Nov 2017 16:28:13 +0100
> > > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > > >    
> > > > > > +Nicolas
> > > > > > [its email got lost somehow]
> > > > > > Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a
> > > > > > écrit :    
> > > > > > > On Thu, 02 Nov 2017 15:13:47 +0100
> > > > > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > > > > >    
> > > > > > > > Le jeudi 02 novembre 2017 à 13:39 +0100, Boris
> > > > > > > > Brezillon a écrit :    
> > > > > > > > > +Nicolas
> > > > > > > > > 
> > > > > > > > > Hi Richard,
> > > > > > > > > 
> > > > > > > > > On Thu, 02 Nov 2017 12:17:16 +0100
> > > > > > > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > > > > > > >    
> > > > > > > > > > Hi,
> > > > > > > > > > 
> > > > > > > > > > I've got an at91sam9g35-cm based board, with 4
> > > > > > > > > > partition on the
> > > > > > > > > > spi-
> > > > > > > > > > dataflas and 5 partitions on the NAND flash.
> > > > > > > > > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch
> > > > > > > > > > to the new
> > > > > > > > > > NAND
> > > > > > > > > > bindings"),
> > > > > > > > > > the NAND partitions were mtd0-4 and spi-dataflash
> > > > > > > > > > partitions
> > > > > > > > > > mtd5-
> > > > > > > > > > 8.
> > > > > > > > > > 
> > > > > > > > > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch
> > > > > > > > > > to the new
> > > > > > > > > > NAND
> > > > > > > > > > bindings"),
> > > > > > > > > > the spi-dataflash partitions are discovered before
> > > > > > > > > > the NAND
> > > > > > > > > > partitions.
> > > > > > > > > > So NAND partition became mtd4-8 and spi-dataflash
> > > > > > > > > > partition
> > > > > > > > > > mtd0-3.
> > > > > > > > > > 
> > > > > > > > > > This broke some script that relied on the mtd
> > > > > > > > > > numbering.
> > > > > > > > > > 
> > > > > > > > > > Updating those scripts to rely on the mtd device
> > > > > > > > > > name instead
> > > > > > > > > > of
> > > > > > > > > > number is not really a problem. The real problem is
> > > > > > > > > > when an
> > > > > > > > > > older
> > > > > > > > > > script using mtd numbering is run on the new system
> > > > > > > > > > : I expect
> > > > > > > > > > dead
> > > > > > > > > > kittens everywhere !    
> > > > > > > > > 
> > > > > > > > > Crap! That was one of the thing I was afraid of when
> > > > > > > > > changing the
> > > > > > > > > binding: probe order has an impact on ids assigned to
> > > > > > > > > MTD devs,
> > > > > > > > > and
> > > > > > > > > since things are not defined at the same place in the
> > > > > > > > > DT, it
> > > > > > > > > changes
> > > > > > > > > the probe order.
> > > > > > > > >    
> > > > > > > > > > 
> > > > > > > > > > So, I'd like to know if there's a way to force the
> > > > > > > > > > older
> > > > > > > > > > numbering
> > > > > > > > > > ?    
> > > > > > > > > 
> > > > > > > > > Reverting the patches is probably the easiest way
> > > > > > > > > (and it's
> > > > > > > > > easily
> > > > > > > > > backportable). Now, if we want to switch to the new
> > > > > > > > > bindings at
> > > > > > > > > some
> > > > > > > > > point we'll need to support DT aliases for mtd devs:
> > > > > > > > > 
> > > > > > > > > aliases {
> > > > > > > > >         mtdX = &flashpartN;
> > > > > > > > >         mtdY = &flashdevM;
> > > > > > > > > };
> > > > > > > > > 
> > > > > > > > > The problem with this solution is that it only works
> > > > > > > > > if all
> > > > > > > > > partitions
> > > > > > > > > are defined in the DT, which is not always the case
> > > > > > > > > (they can be
> > > > > > > > > defined
> > > > > > > > > on the command line with mtdparts=).    
> > > > > > > > 
> > > > > > > > Yes, and if they are different from the ones declared
> > > > > > > > in
> > > > > > > > at91sam9x5cm.dtsi, they are likely defined with
> > > > > > > > mtdparts=, since
> > > > > > > > AFAIK,
> > > > > > > > we can't remove a declared partitionning.
> > > > > > > > 
> > > > > > > > I'll disable the ebi and switch back to the old binding
> > > > > > > > in my dts
> > > > > > > > for
> > > > > > > > now.    
> > > > > > > > >    
> > > > > > > > > > (I tried poking around the DTS without succès).
> > > > > > > > > > 
> > > > > > > > > > any idea ?    
> > > > > > > > > 
> > > > > > > > > I don't have a perfect solution, but the problem you
> > > > > > > > > report
> > > > > > > > > clearly
> > > > > > > > > shows that relying on MTD numbering is unsafe and
> > > > > > > > > should be
> > > > > > > > > avoided.    
> > > > > > > > 
> > > > > > > > Clearly, but who doesn't ? ;)
> > > > > > > >    
> > > > > > > 
> > > > > > > Just had a lengthy discussion with Alexandre, and he
> > > > > > > brought a valid
> > > > > > > point: there has never been any guarantee on MTD
> > > > > > > numbering. Not only
> > > > > > > the order of DT nodes have an impact on the probe order,
> > > > > > > but also the
> > > > > > > order in which drivers are linked when creating the
> > > > > > > kernel image. Yes
> > > > > > > these things usually don't change, but I'm not sure it's
> > > > > > > a good idea
> > > > > > > to let user-space apps think it will never change in the
> > > > > > > future.
> > > > > > > 
> > > > > > > How about fixing the scripts you were referring to
> > > > > > > instead of
> > > > > > > reverting
> > > > > > > the change? What's the blocking point?    
> > > > > > 
> > > > > > I already fixed the user-space scripts (and actually, they
> > > > > > predate the
> > > > > > device-tree era, so at that time, relying on MTD numbering
> > > > > > wasn't so
> > > > > > bad :)).
> > > > > > Anyway, here's the blocking point :
> > > > > > 
> > > > > > We have firmwares with an embedded script to update our
> > > > > > boards. (more
> > > > > > or less a FW + script in a zip file).
> > > > > > Those old firmwares are already in the wild and rely on the
> > > > > > old MTD
> > > > > > numbering (yes, that's bad).
> > > > > > 
> > > > > > 
> > > > > > So, even if all new scripts are corrected in the new
> > > > > > firmwares,
> > > > > > downgrading a board with an old firmware/old script will
> > > > > > brick the
> > > > > > board.
> > > > > > So I'll have to detect that and forbid downgrading.    
> > > > > 
> > > > > Not sure what you refer to when you're talking about 'FW',
> > > > > but I'd
> > > > > expect it to contain a kernel [+ a dtb] + a rootfs, so if
> > > > > you're using
> > > > > an old "FW+update-script", you will still have the old
> > > > > numbering and
> > > > > the old script will work just fine, and if you switch to a
> > > > > newer version
> > > > > of the "FW+update-script" based on a 4.13 kernel+dtb you will
> > > > > anyway
> > > > > have the updated script. Am I missing something?    
> > > > 
> > > > Ok, let's have an example.
> > > > New firmware : kernel
> > > > 4.14+dtb+rootfs+uboot+uboot_env+at91bootstrap+new update
> > > > script.
> > > > Old firmware : kernel 4.11 + dtb + rootfs + uboot +
> > > > uboot_env+at91bootstrap+old update script.
> > > > 
> > > > Let's suppose there's the new firmware on the board (let's call
> > > > it
> > > > 4.14 firmware) :
> > > > MTD0 is the dataflash partition 0 (at91bootstrap)
> > > > MTD1 is the dataflash part1 (uboot)
> > > > MTD2 is the dataflash part2 (ubootenv)
> > > > MTD3 is the dataflash part3 (free space)
> > > > MTD4 is the NAND part 0 (dtb)
> > > > MTD5 is the NAND part 1 (kernel)
> > > > MTD6 is the NAND part 2 (UBI) <- in this one, there're 3 ubifs
> > > > volumes
> > > > : rootfs/rootfs2/data
> > > > 
> > > > The thing is, the update script runs in user-space and updates
> > > > the
> > > > kernel, dtb, uboot, bootstrap and flashes the rootfs2.
> > > > (on next boot, the rootfs2/rootfs will be atomically swapped)
> > > > So, when downgrading, the old update script is executed on the
> > > > board,
> > > > under the 4.14 firmware, thinking that MTD0 is the NAND part0
> > > > (dtb),
> > > > while it is actually the dataflash part0 (bootstrap).  
> > > > => the bootstrap is erased and replaced by the dtb (well,
> > > > actually, it    
> > > > won't even be like that since there will be a mismatch between
> > > > nandwrite/flash_part).  
> > > 
> > > Can you re-generate zip archives for old versions? If you can
> > > maybe it
> > > would be simpler to just embed the new update script (assuming
> > > this
> > > script works fine with both old and new FW) in old FW archives.
> > >  
> > 
> > No sure, I've totally understand the issue, if not sorry for the
> > noise!
> > 
> > Would it be possible to use some udev rules to create some symbolic
> > links
> > in /dev based on ATTRS{name}, the mtd partition names?
> > 
> > something like:
> > /dev/mtd-at91bootstrap -> /dev/mtd0
> > /dev/mtd-uboot -> /dev/mtd1
> > /dev/mtd-ubootenv -> /dev/mtd2
> > /dev/mtd-free -> /dev/mtd3
> > /dev/mtd-dtb -> /dev/mtd4
> > /dev/mtd-kernel -> /dev/mtd5
> > /dev/mtd-ubi -> /dev/mtd6
> 
> Yep, we should definitely have a udev rule populating
> a /dev/mtd/by-name/ directory, just like there is a /dev/disk/by-
> uuid.
Yes, udev rules can be a solution.
And I agree on the /dev/mtd/by-name/ directory, that would be a nice
thing.

> 
> > 
> > Then if the new update script only uses symbolic names, it should
> > work with
> > both linux 4.11 and 4.14 kernels.
> > 
> > But I think I didn't totally understand why/how the old update
> > script would
> > be run under the new kernel :p
> 
> The problem is that the update script in embedded in the archive
> containing image(s) to flash, so old archives still have the old
> script, which means, if you try to downgrade to an older version from
> a
> new version you're screwed because it will use /dev/mtdX directly
> without checking if this is the right partition.

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Re: sam9x5: MTD numbering changed

[Richard Genoud]

Le jeudi 02 novembre 2017 à 18:58 +0100, Boris Brezillon a écrit :
> On Thu, 2 Nov 2017 18:36:35 +0100
> Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> 
> > 2017-11-02 16:45 GMT+01:00 Boris Brezillon <boris.brezillon@free-el
> > ectrons.com>:
> > > On Thu, 02 Nov 2017 16:28:13 +0100
> > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > >  
> > > > +Nicolas
> > > > [its email got lost somehow]
> > > > Le jeudi 02 novembre 2017 à 16:09 +0100, Boris Brezillon a
> > > > écrit :  
> > > > > On Thu, 02 Nov 2017 15:13:47 +0100
> > > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > > >  
> > > > > > Le jeudi 02 novembre 2017 à 13:39 +0100, Boris Brezillon a
> > > > > > écrit :  
> > > > > > > +Nicolas
> > > > > > > 
> > > > > > > Hi Richard,
> > > > > > > 
> > > > > > > On Thu, 02 Nov 2017 12:17:16 +0100
> > > > > > > Richard Genoud <richard.genoud-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > > > > >  
> > > > > > > > Hi,
> > > > > > > > 
> > > > > > > > I've got an at91sam9g35-cm based board, with 4
> > > > > > > > partition on the
> > > > > > > > spi-
> > > > > > > > dataflas and 5 partitions on the NAND flash.
> > > > > > > > Before commit 1004a2977bdc ("ARM: dts: at91: Switch to
> > > > > > > > the new
> > > > > > > > NAND
> > > > > > > > bindings"),
> > > > > > > > the NAND partitions were mtd0-4 and spi-dataflash
> > > > > > > > partitions
> > > > > > > > mtd5-
> > > > > > > > 8.
> > > > > > > > 
> > > > > > > > Since commit 1004a2977bdc ("ARM: dts: at91: Switch to
> > > > > > > > the new
> > > > > > > > NAND
> > > > > > > > bindings"),
> > > > > > > > the spi-dataflash partitions are discovered before the
> > > > > > > > NAND
> > > > > > > > partitions.
> > > > > > > > So NAND partition became mtd4-8 and spi-dataflash
> > > > > > > > partition
> > > > > > > > mtd0-3.
> > > > > > > > 
> > > > > > > > This broke some script that relied on the mtd
> > > > > > > > numbering.
> > > > > > > > 
> > > > > > > > Updating those scripts to rely on the mtd device name
> > > > > > > > instead
> > > > > > > > of
> > > > > > > > number is not really a problem. The real problem is
> > > > > > > > when an
> > > > > > > > older
> > > > > > > > script using mtd numbering is run on the new system : I
> > > > > > > > expect
> > > > > > > > dead
> > > > > > > > kittens everywhere !  
> > > > > > > 
> > > > > > > Crap! That was one of the thing I was afraid of when
> > > > > > > changing the
> > > > > > > binding: probe order has an impact on ids assigned to MTD
> > > > > > > devs,
> > > > > > > and
> > > > > > > since things are not defined at the same place in the DT,
> > > > > > > it
> > > > > > > changes
> > > > > > > the probe order.
> > > > > > >  
> > > > > > > > 
> > > > > > > > So, I'd like to know if there's a way to force the
> > > > > > > > older
> > > > > > > > numbering
> > > > > > > > ?  
> > > > > > > 
> > > > > > > Reverting the patches is probably the easiest way (and
> > > > > > > it's
> > > > > > > easily
> > > > > > > backportable). Now, if we want to switch to the new
> > > > > > > bindings at
> > > > > > > some
> > > > > > > point we'll need to support DT aliases for mtd devs:
> > > > > > > 
> > > > > > > aliases {
> > > > > > >         mtdX = &flashpartN;
> > > > > > >         mtdY = &flashdevM;
> > > > > > > };
> > > > > > > 
> > > > > > > The problem with this solution is that it only works if
> > > > > > > all
> > > > > > > partitions
> > > > > > > are defined in the DT, which is not always the case (they
> > > > > > > can be
> > > > > > > defined
> > > > > > > on the command line with mtdparts=).  
> > > > > > 
> > > > > > Yes, and if they are different from the ones declared in
> > > > > > at91sam9x5cm.dtsi, they are likely defined with mtdparts=,
> > > > > > since
> > > > > > AFAIK,
> > > > > > we can't remove a declared partitionning.
> > > > > > 
> > > > > > I'll disable the ebi and switch back to the old binding in
> > > > > > my dts
> > > > > > for
> > > > > > now.  
> > > > > > >  
> > > > > > > > (I tried poking around the DTS without succès).
> > > > > > > > 
> > > > > > > > any idea ?  
> > > > > > > 
> > > > > > > I don't have a perfect solution, but the problem you
> > > > > > > report
> > > > > > > clearly
> > > > > > > shows that relying on MTD numbering is unsafe and should
> > > > > > > be
> > > > > > > avoided.  
> > > > > > 
> > > > > > Clearly, but who doesn't ? ;)
> > > > > >  
> > > > > 
> > > > > Just had a lengthy discussion with Alexandre, and he brought
> > > > > a valid
> > > > > point: there has never been any guarantee on MTD numbering.
> > > > > Not only
> > > > > the order of DT nodes have an impact on the probe order, but
> > > > > also the
> > > > > order in which drivers are linked when creating the kernel
> > > > > image. Yes
> > > > > these things usually don't change, but I'm not sure it's a
> > > > > good idea
> > > > > to let user-space apps think it will never change in the
> > > > > future.
> > > > > 
> > > > > How about fixing the scripts you were referring to instead of
> > > > > reverting
> > > > > the change? What's the blocking point?  
> > > > 
> > > > I already fixed the user-space scripts (and actually, they
> > > > predate the
> > > > device-tree era, so at that time, relying on MTD numbering
> > > > wasn't so
> > > > bad :)).
> > > > Anyway, here's the blocking point :
> > > > 
> > > > We have firmwares with an embedded script to update our boards.
> > > > (more
> > > > or less a FW + script in a zip file).
> > > > Those old firmwares are already in the wild and rely on the old
> > > > MTD
> > > > numbering (yes, that's bad).
> > > > 
> > > > 
> > > > So, even if all new scripts are corrected in the new firmwares,
> > > > downgrading a board with an old firmware/old script will brick
> > > > the
> > > > board.
> > > > So I'll have to detect that and forbid downgrading.  
> > > 
> > > Not sure what you refer to when you're talking about 'FW', but
> > > I'd
> > > expect it to contain a kernel [+ a dtb] + a rootfs, so if you're
> > > using
> > > an old "FW+update-script", you will still have the old numbering
> > > and
> > > the old script will work just fine, and if you switch to a newer
> > > version
> > > of the "FW+update-script" based on a 4.13 kernel+dtb you will
> > > anyway
> > > have the updated script. Am I missing something?  
> > 
> > Ok, let's have an example.
> > New firmware : kernel
> > 4.14+dtb+rootfs+uboot+uboot_env+at91bootstrap+new update script.
> > Old firmware : kernel 4.11 + dtb + rootfs + uboot +
> > uboot_env+at91bootstrap+old update script.
> > 
> > Let's suppose there's the new firmware on the board (let's call it
> > 4.14 firmware) :
> > MTD0 is the dataflash partition 0 (at91bootstrap)
> > MTD1 is the dataflash part1 (uboot)
> > MTD2 is the dataflash part2 (ubootenv)
> > MTD3 is the dataflash part3 (free space)
> > MTD4 is the NAND part 0 (dtb)
> > MTD5 is the NAND part 1 (kernel)
> > MTD6 is the NAND part 2 (UBI) <- in this one, there're 3 ubifs
> > volumes
> > : rootfs/rootfs2/data
> > 
> > The thing is, the update script runs in user-space and updates the
> > kernel, dtb, uboot, bootstrap and flashes the rootfs2.
> > (on next boot, the rootfs2/rootfs will be atomically swapped)
> > So, when downgrading, the old update script is executed on the
> > board,
> > under the 4.14 firmware, thinking that MTD0 is the NAND part0
> > (dtb),
> > while it is actually the dataflash part0 (bootstrap).
> > => the bootstrap is erased and replaced by the dtb (well, actually,
> > it  
> > won't even be like that since there will be a mismatch between
> > nandwrite/flash_part).
> 
> Can you re-generate zip archives for old versions? If you can maybe
> it
> would be simpler to just embed the new update script (assuming this
> script works fine with both old and new FW) in old FW archives.

Yes, I can do that.
I'll still have to prevent old script from running on a new version,
but that will work.

> 
> > 
> > It's not a huge big deal since I have another way to flash all
> > partitions from uboot, but this can't be done remotely.
> > 
> > 
> > >  
> > > > 
> > > > That's not the end of the world, but if I can find a trick to
> > > > prevent
> > > > it, I'll be happier !
> > > > 
> > > >  
> 
> 
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