Re: [PATCH v2] cirrus-logic-framebuffer-i2c-support.patch

Antonino A. Daplas
2006-07-10T15:18:58Z

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