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 5C60420B1EC; Mon, 3 Feb 2025 16:34:28 +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=1738600469; cv=none; b=uNEd7w06ffSBas98ellLAgB5WOFYimLU4a0GaaLUcVw2HupdTLrq/1b5DkXKYBKUh+R0fiQNYqOvekAMEZsq4O9Y9PGuuazgNVSzHRwMlXMxiSmehKA/zdRNz7+L/7y5xiCrON/7PNg8c8xQGsYJeIzjbjQ3sRB137DxVI1TCFU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738600469; c=relaxed/simple; bh=QzAhLfygH1VmeI6a93oc1pLJc+Tl3u3i4HIkwZDVWdY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sgdDBATogLe/h+Q+qbX8cR1pWMNwBo7m5+vhbARnVmq5PGAyZ+SH1arKkgFuopCVD2zG4LPiZ0tcZ+61hpbnnAtiet5UQtkRid7otUd/U1HWBfqTCh0SlLkQKAwrjchqgKa2X1dCq+LGkOcPj2Pz2aI3FUH8wht43CBZr2uK0BM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CjtwPXwD; 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="CjtwPXwD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 36F7CC4CED2; Mon, 3 Feb 2025 16:34:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738600468; bh=QzAhLfygH1VmeI6a93oc1pLJc+Tl3u3i4HIkwZDVWdY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=CjtwPXwDLEP0VrI4vKCdbZ5sa0hagVfZ6VCFikPp3SIMjIT+bd+8zP61i4gnuuaGe tyUHQVeU2MOtAfxQ40rKhVyJUw6URKi3RSBZOL2YgezMtkfHA9kS951Om2RhNxIS3w 5CnGn/QNR0XTrcUcaXFgZD+jswBRTnlKwDbQnniB2ggyYJ2DPDCeKohSVNCBkHJnda YH3iovjmXPMLXxFdNYYnLiIlzULAvDveZhf48NhLB2eUe/7MLnFcheO0cfnuQHAodH 1DMVIL7oqN1Kmx6obxz0f2s09WLl/lxVfdFJtsra+enPJ1HIyEtV0i4nWXWFQTjRcO hBiS65sjjbRaQ== Message-ID: <0708dbf1-5914-4372-9df2-5cf590fd7bd6@kernel.org> Date: Mon, 3 Feb 2025 17:34:20 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v10 1/2] media: iris: introduce helper module to select video driver To: Dmitry Baryshkov , Johan Hovold Cc: Abhinav Kumar , Dikshita Agarwal , quic_vgarodia@quicinc.com, mchehab@kernel.org, robh@kernel.org, krzk+dt@kernel.org, p.zabel@pengutronix.de, hverkuil@xs4all.nl, sebastian.fricke@collabora.com, bryan.odonoghue@linaro.org, neil.armstrong@linaro.org, nicolas@ndufresne.ca, u.kleine-koenig@baylibre.com, stefan.schmidt@linaro.org, lujianhua000@gmail.com, linux-arm-msm@vger.kernel.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, krzysztof.kozlowski@linaro.org References: <20250128080429.3911091-1-quic_dikshita@quicinc.com> <20250128080429.3911091-2-quic_dikshita@quicinc.com> <5070e1f1-914b-4654-88ef-3566e3eee9ca@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 03/02/2025 16:16, Dmitry Baryshkov wrote: > On Mon, Feb 03, 2025 at 09:22:51AM +0100, Johan Hovold wrote: >> On Fri, Jan 31, 2025 at 10:44:28AM -0800, Abhinav Kumar wrote: >>> On 1/29/2025 2:44 AM, Krzysztof Kozlowski wrote: >>>> On 28/01/2025 09:04, Dikshita Agarwal wrote: >> >>>>> diff --git a/drivers/media/platform/qcom/iris/iris_probe.c b/drivers/media/platform/qcom/iris/iris_probe.c >>>>> index 954cc7c0cc97..276461ade811 100644 >>>>> --- a/drivers/media/platform/qcom/iris/iris_probe.c >>>>> +++ b/drivers/media/platform/qcom/iris/iris_probe.c >>>>> @@ -196,6 +196,9 @@ static int iris_probe(struct platform_device *pdev) >>>>> u64 dma_mask; >>>>> int ret; >>>>> >>>>> + if (!video_drv_should_bind(&pdev->dev, true)) >>>>> + return -ENODEV; >>>> >>>> Wouldn't it mark the probe as failed and cause dmesg regressions? >> >> No, this is perfectly fine. Probe can return -ENODEV and driver core >> will continue with any further matches. >> >>>>> +#if !IS_REACHABLE(CONFIG_VIDEO_QCOM_VENUS) || !IS_REACHABLE(CONFIG_VIDEO_QCOM_IRIS) >>>>> +bool video_drv_should_bind(struct device *dev, bool is_iris_driver) >>>>> +{ >>>>> + /* If just a single driver is enabled, use it no matter what */ >>>>> + return true; >>>>> +} >>>>> + >>>>> +#else >>>>> +static bool prefer_venus = true; >>>>> +MODULE_PARM_DESC(prefer_venus, "Select whether venus or iris driver should be preferred"); >>>>> +module_param(prefer_venus, bool, 0444); >>>> >>>> >>>> The choice of driver is by module blacklisting, not by failing probes. >>>> >>>> I don't understand why this patchset is needed and neither commit msg >>>> nor above longer code comment explain me that. Just blacklist the module. >> >>> Summarizing the discussion with myself, Krzysztof and Dmitry: >>> >>> 1) module blacklisting solution will not be ideal if users want to have >>> both venus and iris or either of them built-in >> >> Module blacklisting is not the way to go, you shouldn't have two drivers >> racing to bind to the same device ever. >> >>> 2) with current approach, one of the probes (either venus or iris) will >>> certainly fail as video_drv_should_bind() will fail for one of them. >>> This can be considered as a regression and should not happen. >> >> How can that be a regression? One driver must fail to probe (see above). > > I also don't think that it's a regression. I think Krzysztof was > concerned about the 'failed to bind' messages in dmesg. I never used word "regression" alone. I said "dmesg regression", which means you have error in logs or any system facility which provides you self-information about device probe history. I don't remember if -ENODEV leads to any printks, so maybe I am wrong here, but regardless normal and expected operation of a driver should never result in -ERRNO, except deferred probe of course. Best regards, Krzysztof