linux-kernel - Re: [mmc] alternative TI FM MMC/SD driver for 2.6.21-rc7

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Date:	Fri, 20 Apr 2007 12:22:13 +0300
From:	Sergey Yanovich <ynvich@...il.com>
To:	unlisted-recipients:; (no To-header on input)
CC:	linux-kernel@...r.kernel.org
Subject: Re: [mmc] alternative TI FM MMC/SD driver for 2.6.21-rc7

Hi,

Arnd Bergmann wrote:
> As very general comments, you should have the maintainer of the subsystem
> (Pierre in this case) on Cc when posting a driver, and you should include
> the patch inline in your mail, see Documentation/SubmittingPatches.
>   
I have cc'ed both Pierre and Alex, but my first message was blocked
by the list as it contained html.

For inlinning, this is my first kernel patch. I have just followed
http://www.tux.org/lkml/#s2-2.
> You should include the Makefile and Kconfig changes in the same patch/mail,
> no point splitting these out.
>   
Once again it was an advise from http://www.tux.org/lkml/#s1-10. 
<http://www.tux.org/lkml/#s1-10>
> Don't define your own DBG macro, instead use the predefined dev_dbg()
> that has a similar definition.
>   
Somewhere in 0.5-0.6 version this driver has issues with timeouts , 
which were
revealing in a non-debug kernel builds only . So this was a nessecity. I 
will purge
them now.
> Your mmc_tifm_irq_chip() function does a _very_ long delay of 100
> miliseconds. This is normally not acceptable, since it is a noticeable
> time in which the system is completely unresponsive. Maybe you can convert
> the tasklet to a workqueue, which lets you call msleep instead of mdelay.
>   
This is done intentionally to prevent a race condition when a card is 
removed
and immediately reinserted. There may be a more complicated way to solve 
this
issue, but didn't think about them. This only happens when an MMC/SD 
card is
inserted/removed. And it takes at least as long to process the event in 
other
parts of subsystem.
> Your use of pci_map_sg() looks wrong, you simply can't assume that the
> return value is '1' in general. I've stumbled over that same problem
> in the sdhci driver, so it may be inherent to the mmc layer and not
> be driver specific.
>   
This is taken as is from [tifm_sd]. I suppose this relates to a hardware
limitation:

+	mmc->max_hw_segs = 1;
+	mmc->max_phys_segs = 1;


Best regards,
Sergey
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