Re: [PATCH 1/3] mtd: cmdlinepart: make the partitions rule more strict

[Huang Shijie <b32955@freescale.com>]

于 2012年09月04日 19:48, Shmulik Ladkani 写道:
> On Mon, 03 Sep 2012 18:35:44 +0300 Artem Bityutskiy<dedekind1@gmail.com>  wrote:
>> With the logic I suggested, for this case what I said would basically:
>>
>> 1. Sort. This leads to
>>
>> 100m@100m(kernel)
>> 1g@200m(rootfs)
>> 100m(boot)
>>
>> "OFFSET_CONTINOUS" is always the largest and will be at the end when
>> sorting.
>>
>> 2. Verification.
>>
>> We verify for overlaps and gaps. And refuse this one.
> Artem, Huang,
>
> Sorry for the long delay, got busy with urgent matters (found out I need
> to go thru some surgery), I will probably not be available in the
> upcoming days, but I've read the correspondance and wanted to share my
> two cents...
>
> My POV is that sorting and verification is not needed, is troublesome,
> and might affect users in ways they don't expect.
>
> So far, mtdparts commandline parsing has been very lenient and liberal.
> I think we should keep this approach; give the user the flexibility,
> he'll be responsible to provide meaningful cmdline parts for his
> system.
>
> Actually, Huang's initial complaint was that 'parse_cmdline_partitions'
> was too strict - the truncated partition was not registered!
>
> Now, philosophy aside, let's talk about some usecases that might break.
>
> I remember overlapping partitions (more precisely, partition that is a
> subset of another) being common in some embedded systems, where the
> "rootfs" and "kernel" partitions are a subset of the "overall image"
> partition.
> Why break this? if users enjoy the flexibility, and careful not to
> create silly partitions, I'm in favor of keeping the flexibility.
>
> Same goes for sorting.
> If one has a system hacked to work with mtd0 hardcodedly, but mtd0's
> physical location is somewhere at the end of the device, why reorder the
> partitions enumeration affecting this system?
>
> I'd say keep it simple and flexible.
yes, it's really simple and flexible.
But I think it's not wise to export the 0-size partition to user.
The user may confused at this.

And the mtd-utils, such as mtd-info/mtd-debug, do they can work with a 
0-size partition?

thanks
Huang Shijie

> I trust the user to provide meaningful partitions in the cmdline.
>
> Anyways, please consider this approach.
>
> My patch suggestion might look as (and might need some rework):
>
> diff --git a/drivers/mtd/cmdlinepart.c b/drivers/mtd/cmdlinepart.c
> index 17b0bd4..f5df613 100644
> --- a/drivers/mtd/cmdlinepart.c
> +++ b/drivers/mtd/cmdlinepart.c
> @@ -324,7 +324,6 @@ static int parse_cmdline_partitions(struct mtd_info *master,
>                                                 "%s: partitioning exceeds flash size, truncating\n",
>                                                 part->mtd_id);
>                                          part->parts[i].size = master->size - offset;
> -                                       part->num_parts = i;
>                                  }
>                                  offset += part->parts[i].size;
>                          }
>
> Regards,
> Shmulik
>
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