linux-kernel - Re: [RFC PATCH] RFC: drivers: gpio: helper for generic pin IRQ handling

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Message-ID: <0c16ab33-f87f-b32d-53d0-a44a5fecd6dc@ti.com>
Date:   Tue, 8 Dec 2020 18:18:17 +0200
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        <joyce.ooi@...el.com>, Andrew Jeffery <andrew@...id.au>,
        Hoan Tran <hoan@...amperecomputing.com>,
        Serge Semin <fancer.lancer@...il.com>, <orsonzhai@...il.com>,
        <baolin.wang7@...il.com>, <zhang.lyra@...il.com>,
        Andy Shevchenko <andy@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Jun Nie <jun.nie@...aro.org>, Shawn Guo <shawnguo@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>
Subject: Re: [RFC PATCH] RFC: drivers: gpio: helper for generic pin IRQ
 handling



On 08/12/2020 16:38, Andy Shevchenko wrote:
> On Tue, Dec 8, 2020 at 4:19 PM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
>> On Tue, Dec 8, 2020 at 4:14 PM Enrico Weigelt, metux IT consult
>> <info@...ux.net> wrote:
>>>
>>> Many gpio drivers already use gpiolib's builtin irqchip handling
>>> (CONFIG_GPIOLIB_IRQCHIP), but still has some boilerplate for retrieving
>>> the actual Linux IRQ number and calling into the generic handler.
>>> That boilerplate can be reduced by moving that into a helper function.
>>>
>>> This is an RFC patch to outline how that could be done. Note: it's
>>> completely untested yet.
>>>
>>> Several drivers still have their completely IRQ own implementation and
>>> thus can't be converted yet. Some of them perhaps could be changed to
>>> store their irq domain in the struct gpio, so the new helper could
>>> also be used for those.
>>>
>>> Having all GPIO drivers doing their IRQ management entirely through the
>>> GPIO subsystem (eg. never calling generic_handle_irq() and using the builtin
>>> IRQ handling) would also allow a more direct (eg. callback-based) pin change
>>> notification for GPIO consumers, that doesn't involve registering them as
>>> generic IRQ handlers.

Above part makes me worry - why?

>>>
>>> Further reduction of boilerplate could be achieved by additional helpers
>>> for common patterns like for_each_set_bit() loops on irq masks.
>>
>> Have you able to test them all?
>> As the PCA953x case showed us this is not so simple, besides the name
>> which sucks — we don't *raise* and IRQ we *handle* it.
>>
>> NAK.
> 
> To be on constructive side what I think can help here:
> - split patch on per driver basis (and first patch is a simple
> introduction of new API)
> - rename function
> - in each new per-driver patch explain what is the difference in behaviour
> - test as many as you can and explain in a cover letter what has been
> done and what are the expectations on the ones that you weren't able
> to test.
> 

agree.

-- 
Best regards,
grygorii