Re: [PATCH v6 07/14] media: mediatek: vcodec: send share memory address to vcp

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Unconditional increase in firmware IPC message size may break backwards compatibility with older SCP/VPU firmware.
--

--- Patch [7]: [PATCH v6 07/14] media: mediatek: vcodec: send share memory address to vcp ---
commit 84b64e642819aa5202009e5076e47823645bcbc0
Author: Kyrie Wu <kyrie.wu@mediatek.com>

media: mediatek: vcodec: send share memory address to vcp

This commit updates the AP to VPU initialization message by adding a shared
memory address field. It is used specifically for the VCP architecture where
shared memory is allocated in the kernel rather than reserved in the VPU.

> diff --git a/drivers/media/platform/mediatek/vcodec/decoder/vdec_ipi_msg.h b/drivers/media/platform/mediatek/vcodec/decoder/vdec_ipi_msg.h
> index 47070be2a9914..097561a1efdcf 100644
> --- a/drivers/media/platform/mediatek/vcodec/decoder/vdec_ipi_msg.h
> +++ b/drivers/media/platform/mediatek/vcodec/decoder/vdec_ipi_msg.h

[ ... ]

>  struct vdec_ap_ipi_init {
>  	uint32_t msg_id;
>  	u32 codec_type;
>  	uint64_t ap_inst_addr;
> +	u64 shared_iova;
>  };

[ ... ]

> diff --git a/drivers/media/platform/mediatek/vcodec/decoder/vdec_vpu_if.c b/drivers/media/platform/mediatek/vcodec/decoder/vdec_vpu_if.c
> index cdb673e6b4770..3a10b32be0945 100644
> --- a/drivers/media/platform/mediatek/vcodec/decoder/vdec_vpu_if.c
> +++ b/drivers/media/platform/mediatek/vcodec/decoder/vdec_vpu_if.c
> @@ -236,6 +236,8 @@ int vpu_dec_init(struct vdec_vpu_inst *vpu)
>  	msg.msg_id = AP_IPIMSG_DEC_INIT;
>  	msg.ap_inst_addr = (unsigned long)vpu;
>  	msg.codec_type = vpu->codec_type;
> +	if (mtk_vcodec_fw_get_type(vpu->ctx->dev->fw_handler) == VCP)
> +		msg.shared_iova = vpu->ctx->dev->fw_handler->vcp->iova_addr;
>  
>  	mtk_vdec_debug(vpu->ctx, "vdec_inst=%p", vpu);

[Severity: Medium]
Does this unconditional size increase break backwards compatibility with older
SCP/VPU firmware?

By adding shared_iova to struct vdec_ap_ipi_init, the struct size increases
from 16 bytes to 24 bytes. Directly after this diff hunk in vpu_dec_init(),
the message is sent to the firmware using the full sizeof(msg):

err = vcodec_vpu_send_msg(vpu, (void *)&msg, sizeof(msg));

If older firmware expects a strictly sized 16-byte initialization message,
could sending 24 bytes unconditionally cause the initialization to fail and
render the video decoder unusable on existing non-VCP devices?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260720012056.1026551-1-kyrie.wu@mediatek.com?part=7