Re: [RFC PATCH v10 1/2] media: iris: introduce helper module to select video driver

[Krzysztof Kozlowski <krzk@kernel.org>]

On 28/01/2025 09:04, Dikshita Agarwal wrote:
> Introduce a helper module with a kernel param to select between
> venus and iris drivers for platforms supported by both drivers.
> 
> Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
> ---
>  drivers/media/platform/qcom/Makefile          |  1 +
>  drivers/media/platform/qcom/iris/iris_core.h  |  1 +
>  drivers/media/platform/qcom/iris/iris_probe.c |  3 +
>  drivers/media/platform/qcom/venus/core.c      |  5 ++
>  .../platform/qcom/video_drv_helper/Makefile   |  4 ++
>  .../qcom/video_drv_helper/video_drv_helper.c  | 70 +++++++++++++++++++
>  .../qcom/video_drv_helper/video_drv_helper.h  | 11 +++
>  7 files changed, 95 insertions(+)
>  create mode 100644 drivers/media/platform/qcom/video_drv_helper/Makefile
>  create mode 100644 drivers/media/platform/qcom/video_drv_helper/video_drv_helper.c
>  create mode 100644 drivers/media/platform/qcom/video_drv_helper/video_drv_helper.h
> 
> diff --git a/drivers/media/platform/qcom/Makefile b/drivers/media/platform/qcom/Makefile
> index ea2221a202c0..15accde3bd67 100644
> --- a/drivers/media/platform/qcom/Makefile
> +++ b/drivers/media/platform/qcom/Makefile
> @@ -2,3 +2,4 @@
>  obj-y += camss/
>  obj-y += iris/
>  obj-y += venus/
> +obj-y += video_drv_helper/
> diff --git a/drivers/media/platform/qcom/iris/iris_core.h b/drivers/media/platform/qcom/iris/iris_core.h
> index 37fb4919fecc..7108e751ff88 100644
> --- a/drivers/media/platform/qcom/iris/iris_core.h
> +++ b/drivers/media/platform/qcom/iris/iris_core.h
> @@ -107,5 +107,6 @@ struct iris_core {
>  
>  int iris_core_init(struct iris_core *core);
>  void iris_core_deinit(struct iris_core *core);
> +extern bool video_drv_should_bind(struct device *dev, bool is_iris_driver);
>  
>  #endif
> 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?

> +
>  	core = devm_kzalloc(&pdev->dev, sizeof(*core), GFP_KERNEL);
>  	if (!core)
>  		return -ENOMEM;
> diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
> index 77d48578ecd2..b38be7812efe 100644
> --- a/drivers/media/platform/qcom/venus/core.c
> +++ b/drivers/media/platform/qcom/venus/core.c
> @@ -369,12 +369,17 @@ static int venus_add_dynamic_nodes(struct venus_core *core)
>  static void venus_remove_dynamic_nodes(struct venus_core *core) {}
>  #endif
>  
> +extern bool video_drv_should_bind(struct device *dev, bool is_iris_driver);

You just defined it in the header. Why is this here?

> +
>  static int venus_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
>  	struct venus_core *core;
>  	int ret;
>  
> +	if (!video_drv_should_bind(&pdev->dev, false))
> +		return -ENODEV;

Same problems - d,esg regression.

> +
>  	core = devm_kzalloc(dev, sizeof(*core), GFP_KERNEL);
>  	if (!core)
>  		return -ENOMEM;
> diff --git a/drivers/media/platform/qcom/video_drv_helper/Makefile b/drivers/media/platform/qcom/video_drv_helper/Makefile
> new file mode 100644
> index 000000000000..82567e0392fb
> --- /dev/null
> +++ b/drivers/media/platform/qcom/video_drv_helper/Makefile
> @@ -0,0 +1,4 @@

Missing SPDX

> +# Makefile for Video driver helper
> +
> +obj-m := video_drv_helper.o
> +
> diff --git a/drivers/media/platform/qcom/video_drv_helper/video_drv_helper.c b/drivers/media/platform/qcom/video_drv_helper/video_drv_helper.c
> new file mode 100644
> index 000000000000..9009c2906e54
> --- /dev/null
> +++ b/drivers/media/platform/qcom/video_drv_helper/video_drv_helper.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2025 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +
> +#include "video_drv_helper.h"
> +
> +/* The venus driver supports only hfi gen1 to communicate with the firmware while

Use Linux generic coding style comment, not netdev.

> + * the iris driver supports both hfi gen1 and hfi gen2.
> + * The support of hfi gen1 is added to the iris driver with the intention that
> + * it can support old gen1 interface based firmware, while enabling gen2 based future SOCs.
> + * With this, the plan is to migrate older SOCs from venus to iris.
> + * As of now, since the iris driver supports only entry level features and doesn't have
> + * feature parity with the venus driver, a runtime-selection is provided to user via
> + * module parameter 'prefer_venus' to select the driver.
> + * This selection is available only for the SoCs which are supported by both venus
> + * and iris eg: SM8250.
> + * When the feature parity is achieved, the plan is to switch the default to point to
> + * the iris driver, then gradually start removing platforms from venus.
> + * Hardware supported by only venus - 8916, 8996, SDM660, SDM845, SC7180, SC7280
> + * Hardware supported by only iris - SM8550
> + * Hardware supported by both venus and iris - SM8250
> + */
> +
> +#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.

Best regards,
Krzysztof