Re: [PATCH v5 1/2] gpio: add GPO driver for PCA9570

[Andy Shevchenko]

On Tue, Jul 7, 2020 at 5:03 PM Sungbo Eo <mans0n@xxxxxxxxxx> wrote:
> On 20. 7. 6. ìí 9:00, Andy Shevchenko wrote:

...

> But I don't really understand what mutex does here. The driver does not
> need consecutive commands, it only sends/receives only one byte at a
> time. And AFAIK each i2c_smbus function is already protected by a mutex.
> So what should be exactly inside the lock? Should we protect the output
> buffer as well? I'm not an expert on this so please enlighten me.

There are questions, answering them will give you a solution:
- Since we have two functions doing i2c communications, can they
clash? If so, does the i2c framework guarantee the serialisation?
- Since we have a shared resource (buf), can accessors clash? How do
we guarantee serialization?

-- 
With Best Regards,
Andy Shevchenko