linux-kernel - Re: [PATCH v5 0/2] Small devm helper for devm implementations

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Message-ID: <ddfff98f-ebd5-fa25-e4d4-6f3a7cafa132@free.fr>
Date:   Mon, 3 May 2021 14:08:33 +0200
From:   Marc Gonzalez <marc.w.gonzalez@...e.fr>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Russell King <linux@...linux.org.uk>,
        Guenter Roeck <linux@...ck-us.net>,
        Robin Murphy <robin.murphy@....com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 0/2] Small devm helper for devm implementations

On 23/07/2020 17:00, Greg Kroah-Hartman wrote:

> On Tue, Jul 21, 2020 at 09:10:23AM +0200, Marc Gonzalez wrote:
> 
>> On 06/07/2020 21:57, Greg Kroah-Hartman wrote:
>>
>>> Given the lack of testing of the patch, it doesn't seem wise to add
>>> this, right?
>>
>> You're probably not wrong :)
>>
>>> Please get some testing, and some more users, and I'll be glad to
>>> consider it.
>>
>> "Users" == files modified to use the new helper?
> 
> Yes.
> 
>> How many files would you suggest? 3? 5? 10?
> 
> How many do you see that can use it?  I would suggest "all" :)

Hello Greg (and everyone on the CC list),

I'm getting the itch to work on this patch-set again.

To recap: I wrote a tiny devm helper.
It's a trivial wrapper around devres_alloc() + devres_add()
which releases the resource when devres_alloc() fails.
That's all there is to it.

Despite its triviality, the helper allows writing simpler code
in drivers using devm, and generates smaller object code,
so I think it's quite useful.


With all that being said, I'm a bit concerned by Greg's "all" answer.

$ git grep '= devres_alloc' | wc -l
173

$ git grep -c '= devres_alloc' | wc -l
103

There are 173 calls to devres_alloc across 103 files.

It looks (to me) too risky to change everything in a single patch-set.

Perhaps we could define a few frameworks that would get the improvement
as a first step?

$ git grep '= devres_alloc' v5.12 | grep -o 'v5.12:[[:alnum:]]*/[[:alnum:]]*' | uniq -c
      1 v5.12:Documentation/driver
      3 v5.12:drivers/ata
     11 v5.12:drivers/base
      1 v5.12:drivers/bus
      1 v5.12:drivers/char
     13 v5.12:drivers/clk
      1 v5.12:drivers/counter
      4 v5.12:drivers/devfreq
      2 v5.12:drivers/dma
      4 v5.12:drivers/extcon
      2 v5.12:drivers/firmware
      4 v5.12:drivers/fpga
      8 v5.12:drivers/gpio
      1 v5.12:drivers/gpu
      2 v5.12:drivers/hid
      2 v5.12:drivers/hwmon
      3 v5.12:drivers/hwspinlock
      1 v5.12:drivers/i2c
     12 v5.12:drivers/iio
      2 v5.12:drivers/input
      1 v5.12:drivers/interconnect
      5 v5.12:drivers/leds
      1 v5.12:drivers/macintosh
      1 v5.12:drivers/mailbox
      2 v5.12:drivers/media
      2 v5.12:drivers/mfd
      1 v5.12:drivers/mtd
      3 v5.12:drivers/mux
      6 v5.12:drivers/net
      1 v5.12:drivers/ntb
      3 v5.12:drivers/nvmem
      1 v5.12:drivers/of
      4 v5.12:drivers/pci
      5 v5.12:drivers/phy
      3 v5.12:drivers/pinctrl
      2 v5.12:drivers/platform
      4 v5.12:drivers/power
      3 v5.12:drivers/pwm
      6 v5.12:drivers/regulator
      1 v5.12:drivers/remoteproc
      3 v5.12:drivers/reset
      3 v5.12:drivers/spi
      2 v5.12:drivers/staging
      3 v5.12:drivers/thermal
      1 v5.12:drivers/tty
      1 v5.12:drivers/uio
      2 v5.12:drivers/usb
      2 v5.12:drivers/video
      1 v5.12:drivers/watchdog
      1 v5.12:kernel/dma
      1 v5.12:kernel/iomem
      5 v5.12:kernel/irq
      1 v5.12:kernel/reboot
      2 v5.12:kernel/resource
      3 v5.12:lib/devres
      1 v5.12:lib/genalloc
      1 v5.12:mm/dmapool
      2 v5.12:net/devres
      1 v5.12:sound/hda
      6 v5.12:sound/soc
      1 v5.12:tools/testing


Perhaps I could take a look at all the subsystems/frameworks that you maintain, Greg?
What do you think?

Regards.