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

["Antonino A. Daplas" <adaplas@gmail.com>]

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.

David Eger is the author, the last I heard from him was 2 years ago.
But I haven't received that many problem reports on cirrusfb.

However, changes that affect all drivers are my responsibility.
 
> 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).

The only register touched by the i2c code is EEPROM control (CL_SEQR8).
This is never touched by the rest of the cirrusfb code. So I don't
think concurrent access is a problem (unless the hardware has restrictions
such as no other register accesses are allowed while this register is being
accessed). 

The framebuffer layer is serialized by
acquire_console_sem()/release_console_sem(). If you think concurrent access
is a problem, you can always use that.

Tony