Re: [PATCH v2 03/15] accel/qda: Add initial QDA DRM accelerator driver

[Ekansh Gupta]

On 19-08-2026 00:40, Krzysztof Kozlowski wrote:
> On 17/08/2026 06:47, Ekansh Gupta wrote:
>> Add the skeleton of the Qualcomm DSP Accelerator (QDA) driver, a DRM
>> accel driver for the Hexagon DSPs found on Qualcomm SoCs.
>>
>> This patch registers a DRM accel device, exposing a /dev/accel/accelN
>> character device node, and binds it to the RPMsg channel used to reach
>> the DSP. Buffer management, IOMMU context banks and the FastRPC
>> protocol are added by later patches in this series.
>>
>> qda_drv.c / qda_drv.h define the drm_driver ops table, the per-file
>> private state (qda_file_priv) and the main device structure (qda_dev),
>> which embeds drm_device so that it can be recovered with container_of().
>>
>> qda_rpmsg.c binds to the "qcom,fastrpc" compatible via
>> module_rpmsg_driver(), reads the DSP domain name from the "label"
>> device-tree property, and registers the DRM device.
>>
>> Assisted-by: Claude:claude-sonnet-5
>> Signed-off-by: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
>> ---
>> Changes in v2:
>> - Use module_rpmsg_driver() and drop the qda_rpmsg_register()/
>>   _unregister() wrappers, module_init()/module_exit() and
>>   qda_rpmsg.h entirely (Dmitry Baryshkov)
>> - Read the "label" property directly into qdev->dsp_name (Dmitry Baryshkov)
>> - Drop the probe/remove/init log messages (Dmitry Baryshkov)
>> - Return the result of qda_register_device() directly (Dmitry Baryshkov)
>> - Clarify the Kconfig help text (Dmitry Baryshkov)
>> ---
>>  drivers/accel/Kconfig         |  1 +
>>  drivers/accel/Makefile        |  1 +
>>  drivers/accel/qda/Kconfig     | 30 ++++++++++++++++
>>  drivers/accel/qda/Makefile    | 10 ++++++
>>  drivers/accel/qda/qda_drv.c   | 71 ++++++++++++++++++++++++++++++++++++++
>>  drivers/accel/qda/qda_drv.h   | 61 +++++++++++++++++++++++++++++++++
>>  drivers/accel/qda/qda_rpmsg.c | 79 +++++++++++++++++++++++++++++++++++++++++++
>>  7 files changed, 253 insertions(+)
>>
>> diff --git a/drivers/accel/Kconfig b/drivers/accel/Kconfig
>> index bdf48ccafcf2..74ac0f71bc9d 100644
>> --- a/drivers/accel/Kconfig
>> +++ b/drivers/accel/Kconfig
>> @@ -29,6 +29,7 @@ source "drivers/accel/ethosu/Kconfig"
>>  source "drivers/accel/habanalabs/Kconfig"
>>  source "drivers/accel/ivpu/Kconfig"
>>  source "drivers/accel/qaic/Kconfig"
>> +source "drivers/accel/qda/Kconfig"
>>  source "drivers/accel/rocket/Kconfig"
>>  
>>  endif
>> diff --git a/drivers/accel/Makefile b/drivers/accel/Makefile
>> index 1d3a7251b950..58c08dd5f389 100644
>> --- a/drivers/accel/Makefile
>> +++ b/drivers/accel/Makefile
>> @@ -5,4 +5,5 @@ obj-$(CONFIG_DRM_ACCEL_ARM_ETHOSU)	+= ethosu/
>>  obj-$(CONFIG_DRM_ACCEL_HABANALABS)	+= habanalabs/
>>  obj-$(CONFIG_DRM_ACCEL_IVPU)		+= ivpu/
>>  obj-$(CONFIG_DRM_ACCEL_QAIC)		+= qaic/
>> +obj-$(CONFIG_DRM_ACCEL_QDA)		+= qda/
>>  obj-$(CONFIG_DRM_ACCEL_ROCKET)		+= rocket/
>> \ No newline at end of file
> 
> You have trivial patch errors.
newline problem was already there, wasn't introduced as part of this
patch series, so I wasn't sure to fix it here. I can fix this in v3.>
> ...
> 
>> +}
>> +
>> +static const struct of_device_id qda_rpmsg_id_table[] = {
>> +	{ .compatible = "qcom,fastrpc" },
>> +	{},
> 
> Device node with this compatible is already populated, so this looks
> simply wrong or you are adding a duplicated driver.
> 
> That's a no-go, you are supposed to work with existing drivers and grow
> them.
I'll bring the discussion again here, there was a discussion to move the
driver to accel subsystem if we want to support new features/uAPI
changes. Please read [1],[2] threads. The intention is to replace
fastrpc driver with QDA eventually.

Do you suggest adding a different compatible, say "qcom,qda" for this
driver?

Let me know if you have a better suggestion to proceed here.

[1] https://lkml.org/lkml/2024/6/24/479
[2] https://lkml.org/lkml/2024/6/21/1252>
> 
> Best regards,
> Krzysztof