[U-Boot-Users] [Patch 0/9] U-boot-V2: Introduce I2C support for SDP3430

[Sascha Hauer <s.hauer@pengutronix.de>]

On Wed, Jun 18, 2008 at 10:39:30AM -0500, Timur Tabi wrote:
> Menon, Nishanth wrote:
> 
> > Please see U-boot v2 here: 
> 
> Sorry, I didn't notice that your patch is for U-Boot V2.
> 
> > It does not have i2c support. And IMHO, using kernel like i2c addition in U-Boot v2 is appropriate. Why this is not a bloat U-Boot v2?
> 
> If it isn't, then it means that U-Boot V2 will be pretty bloated in general.
> 
> > A) Now, if you just want i2c_transfer without any device interface, you don't need to compile in the CHARDEV.
> > B) Since we use a different linking strategy in U-Boot-v2 which uses gcc link stage to decide which functions be retained and which not, it is pretty neat to see all unused functionality disappear.
> > C) kernel has additional bus and class types which are useful when we think in terms of varied features, in u-boot v2, we don't have a bus and class, just a plain device+driver interface like the kernel + ioctls to allow "apps" to invoke functionality within the driver for the device. Very linux like, call it a micro-linux ;). So kernel i2c architecture fits u_boot v2 better that u-boot v1's architecture.
> > D) U-boot v2 has insmod + rmmod -> though this is still to be fixed, once it is fully functioning, you can loadb just the module feature you need. In fact, you could even have a filesystem with just modules....
> > E) Ofcourse, we work in a single threaded, no interrupt mode in u-boot v2+ don't care for any power management -> more savings there
> 
> Sounds to me like U-Boot V2 is just a repacked Linux kernel.  We could probably
> save ourselves a lot of trouble if we just took the DDR and CPU register
> initialization code in U-Boot and moved it to the kernel.

I've thought about going this way...
But the Linux Kernel typically has around 1M and still you don't have a
shell. U-Boot-v2 is not bigger in code size than V1 with similar
functionality.
You're right, I took a lot of code (and ideas) from the Linux
Kernel, but I'm too unsure if it's a good idea to adopt full-featured
frameworks like I2C from the kernel. BTW U-Boot-v1 does the same thing
with NAND support for example.

Sascha



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