linux-kernel - Re: [PATCH] regmap: slimbus: add support to raw read/writes

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Date:   Thu, 5 Jul 2018 17:13:21 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org
Subject: Re: [PATCH] regmap: slimbus: add support to raw read/writes

On 05/07/18 16:08, Mark Brown wrote:
> On Thu, Jul 05, 2018 at 12:37:00PM +0100, Srinivas Kandagatla wrote:
> 
>> SLIMbus supports upto 16 bytes in value management messages,
>> so add support to raw read/writes upto 16 bytes.
> That's not what raw access is.  It's unmediated access to existing
> registers, not some other thing with completely different register sizes
> which you can't see through the register map.  The intended use is for
> things like fast firmware downloads.  If it's not part of the register
> map we shouldn't be going through regmap to get to it.

Thanks for explaining this in detail.

I think I got it wrong by looking at _regmap_bus_read() implementation 
which calls _regmap_raw_read(), this made me think that read/writes 
callbacks imply raw read/writes. Looks like that is not the case.

These bus read/write callbacks are just simple multiple register 
read/writes.

All am trying to do is support paged registers, which seems to be only 
possible via read/write support at bus level.

Does reg_read/reg_write become redundant if we implement read/write 
callbacks at bus regmap level?

> 
>> Also useful for paged register access on SLIMbus interfaced codecs.
> That needs a bunch more explanation...  in what way does raw access
> relate to paged register maps?
Yes, this is nothing to do with raw access! I got it wrong!
WCD9335 codec has paged registers which is what I need!

I will fix the patch and commit message removing the raw related parts 
and resend.

Does that sound okay?

thanks,
srini