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Message-ID: <44B26FD5.403@pol.net>
Date: Mon, 10 Jul 2006 23:18:45 +0800
From: "Antonino A. Daplas" <adaplas@pol.net>
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To: Krzysztof Halasa <khc@pm.waw.pl>
CC: Jean Delvare <khali@linux-fr.org>, Andrew Morton <akpm@osdl.org>,
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Subject: Re: [PATCH v2] cirrus-logic-framebuffer-i2c-support.patch
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Krzysztof Halasa wrote:
> "Antonino A. Daplas" <adaplas@pol.net> writes:
> 
>> Eventually, I'm the one who's going to maintain the code, most
>> of the drivers in the video directory are practically abandoned. 
> 
> BTW, it's fortunate that you are maintaing it. The I2C code in cirrusfb
> uses vga_wseq() and vga_rseq(). Is it safe WRT races between I2C
> adapter code and fb code? I don't see any locking here, and both
> functions are non-atomic (write merging and posting will not break it,
> but it looks like I need a lock for concurent access).

Correcting myself: vga_wseq() is not a problem in little endian machines
because the 2 single-byte writes are done with a single 2-byte write.
vga_rseq() is not safe though.

I don't know how big a problem this is, reading the i2c bus while the
video mode is changing..., but I agree that it might be worthwhile
to at least lock sequencer access.

Tony