From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 12BC637710; Tue, 30 Jan 2024 08:36:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706603771; cv=none; b=Na/98HyQHPFWnhiAVzMehcsAnVlbJHLfSuyt0DSHZ3yCMXKCq5alEr2tZd9hcVS221YxS56TIKsgI9zInj+3Mz6aPOJ9IV/h55ycUgefMV5RaES6BuKT+fTt3+Cn+US7yh86e9W57w1GXJlJP1FeJeDRPDQ71EYOvn7pD0z8Dww= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706603771; c=relaxed/simple; bh=AiWU2oYV8saTLq8Kb8K4l/kAKUgRW4PIetjMctLm3RI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pv96EwMxdDmtBUm8+U+5lY6ldAl5Zg5eOHZfnvBUNJxFvMPtDAxLQCs9a2mm64moFkGRAH1Zo8SJGmK5cnBuXGFSRDmJpCWtqeeQoWlxfrPZpy/utQoS8yUyl8xGxRQZbq9wyCWnUwrpgo+YvqLJNVt2KZD5SblqoncjL+myxgE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oR2nwdV8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oR2nwdV8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C888C433C7; Tue, 30 Jan 2024 08:36:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706603770; bh=AiWU2oYV8saTLq8Kb8K4l/kAKUgRW4PIetjMctLm3RI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oR2nwdV8RIi7LY+9HMDvPJYE2PXVYdkiqzRDunCFJQdUssS7mvRoUZug1+tPaiCUo VvZru65psnfxPY2uMZ/FlyI99GT/wa/NFd1npOidUX2ncWMWTzOjCEkI5MQurLyq3n MEq4fm9A1MVksAYsPS5yy+rZ1fMYkJNTkVerXHbNljTWAzJ9tiq9JcuO2DPLJ1qOq6 0NPkTWEr5plrCEYhYbLmV5iSlKPdAYx5HIHKpu6AHgFugaAYGGjB7VcW1+1/FCrFfp Q16LBpXK/2qOLMsSMXAF5L5wqInN4s8oNv+4Ak3jqiP8CDYcHil0U9VMvaWadDsdz6 q2xi5QUfwj2vA== Message-ID: Date: Tue, 30 Jan 2024 09:36:01 +0100 Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V3 2/2] pwm: Add GPIO PWM driver Content-Language: en-US To: Linus Walleij Cc: Stefan Wahren , =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= , Rob Herring , Krzysztof Kozlowski , Conor Dooley , andy.shevchenko@gmail.com, Angelo Compagnucci , Philip Howard , linux-pwm@vger.kernel.org, devicetree@vger.kernel.org, linux-gpio@vger.kernel.org, Vincent Whitchurch References: <20240128163630.104725-1-wahrenst@gmx.net> <20240128163630.104725-3-wahrenst@gmx.net> <8f525770-7e39-4bf1-9ad3-803826ffbb1e@kernel.org> From: Krzysztof Kozlowski Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 29/01/2024 14:55, Linus Walleij wrote: > On Mon, Jan 29, 2024 at 10:40 AM Krzysztof Kozlowski wrote: >> On 28/01/2024 17:36, Stefan Wahren wrote: > >>> +MODULE_ALIAS("platform:pwm-gpio"); >> >> You should not need MODULE_ALIAS() in normal cases. If you need it, >> usually it means your device ID table is wrong (e.g. misses either >> entries or MODULE_DEVICE_TABLE()). MODULE_ALIAS() is not a substitute >> for incomplete ID table. > > I was under the impression that MODULE_ALIAS > was something people put in to make platforms using > udev behave better by default, e.g. autoprobing these > devices better (on coldplug for "platform:*"). > > For example: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4f46d6e7e5ffbce0ee1d1a80767fdf45e56cc863 > > But I might have got it all wrong :/ That was 2008 :), but answering to the problem: people put MODULE_ALIAS because they (do not have / forgot / don't want to add)* proper id table for platform devices with MODULE_DEVICE_TABLE. While it works, it does not offer the same scalability as proper ID table and is confusing, because it suggests that driver should be autoloaded by a platform ID, but not matched/bound by platform ID! Such situation is very rare and would deserve a comment anyway. * choose appropriate See also: https://lore.kernel.org/all/?q=f%3Akozlowski+drop+unneeded+module_alias Best regards, Krzysztof