Re: [PATCH v6 4/6] decoder: Add V4L2 stateless H.264 decoder driver

From: Zhentao Guo

Date: Mon Jul 27 2026 - 03:19:36 EST

Hi Krzysztof,

On 24/07/2026 09:04, Zhentao Guo via B4 Relay wrote:
From: Zhentao Guo <zhentao.guo@xxxxxxxxxxx>

Add initial support for V4L2 stateless video decoder
driver on Amlogic S4(S805X2) platform. In phase 1,
it supports 8bit H.264 bitstreams decoding. Currently
only progressive streams are supported.

Signed-off-by: Zhentao Guo <zhentao.guo@xxxxxxxxxxx>
---
MAINTAINERS | 7 +
drivers/media/platform/amlogic/Kconfig | 1 +
drivers/media/platform/amlogic/Makefile | 1 +
drivers/media/platform/amlogic/vdec/Kconfig | 18 +
drivers/media/platform/amlogic/vdec/Makefile | 4 +
drivers/media/platform/amlogic/vdec/TODO | 7 +
drivers/media/platform/amlogic/vdec/aml_vdec.c | 736 +++++++
drivers/media/platform/amlogic/vdec/aml_vdec.h | 33 +
drivers/media/platform/amlogic/vdec/aml_vdec_drv.c | 239 +++
drivers/media/platform/amlogic/vdec/aml_vdec_drv.h | 172 ++
drivers/media/platform/amlogic/vdec/aml_vdec_hw.c | 538 +++++
drivers/media/platform/amlogic/vdec/aml_vdec_hw.h | 157 ++
.../platform/amlogic/vdec/aml_vdec_platform.c | 81 +
.../platform/amlogic/vdec/aml_vdec_platform.h | 46 +
.../media/platform/amlogic/vdec/aml_vdec_tee_fw.c | 240 +++
.../media/platform/amlogic/vdec/aml_vdec_tee_fw.h | 27 +
drivers/media/platform/amlogic/vdec/h264.c | 2067 ++++++++++++++++++++
drivers/media/platform/amlogic/vdec/h264.h | 299 +++
drivers/media/platform/amlogic/vdec/reg_defines.h | 177 ++
19 files changed, 4850 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index a112ce9f0fa0..a27ea19907f9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1423,6 +1423,13 @@ S: Maintained
F: Documentation/devicetree/bindings/spi/amlogic,a4-spisg.yaml
F: drivers/spi/spi-amlogic-spisg.c

+AMLOGIC VDEC DRIVER
+M: Zhentao Guo <zhentao.guo@xxxxxxxxxxx>
+L: linux-media@xxxxxxxxxxxxxxx
You can drop the L:. Subsystem defines it.
OK, got it. I'll drop this.

+S: Maintained
+F: Documentation/devicetree/bindings/media/amlogic,s4-vcodec-dec.yaml
+F: drivers/media/platform/amlogic/vdec/
+
AMPHENOL CHIPCAP 2 DRIVER
M: Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx>
L: linux-hwmon@xxxxxxxxxxxxxxx
diff --git a/drivers/media/platform/amlogic/Kconfig b/drivers/media/platform/amlogic/Kconfig
index 458acf3d5fa8..7c541ac0d0c3 100644
--- a/drivers/media/platform/amlogic/Kconfig
+++ b/drivers/media/platform/amlogic/Kconfig
@@ -4,3 +4,4 @@ comment "Amlogic media platform drivers"

source "drivers/media/platform/amlogic/c3/Kconfig"
source "drivers/media/platform/amlogic/meson-ge2d/Kconfig"
+source "drivers/media/platform/amlogic/vdec/Kconfig"
diff --git a/drivers/media/platform/amlogic/Makefile b/drivers/media/platform/amlogic/Makefile
index c744afcd1b9e..7409de674c0b 100644
--- a/drivers/media/platform/amlogic/Makefile
+++ b/drivers/media/platform/amlogic/Makefile
@@ -2,3 +2,4 @@

obj-y += c3/
obj-y += meson-ge2d/
+obj-y += vdec/
diff --git a/drivers/media/platform/amlogic/vdec/Kconfig b/drivers/media/platform/amlogic/vdec/Kconfig
new file mode 100644
index 000000000000..d392967c7743
--- /dev/null
+++ b/drivers/media/platform/amlogic/vdec/Kconfig
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR MIT)
+
+config VIDEO_AMLOGIC_VDEC
+ tristate "Amlogic Video Decoder Driver"
+ depends on ARCH_MESON || COMPILE_TEST
+ depends on VIDEO_DEV
+ depends on V4L_MEM2MEM_DRIVERS
+ depends on TEE
+ select VIDEOBUF2_DMA_CONTIG
+ select V4L2_H264
+ select V4L2_MEM2MEM_DEV
+ select MESON_CANVAS
+ select MESON_SM
+ help
+ This is a v4l2 driver for Amlogic video decoder driver.
+ This driver is designed to support V4L2 M2M STATELESS
+ interface.
Somehow messed indentation.
I'll fix the indentation problem in the next revision.
...

+err_media_dev_register:
+ v4l2_m2m_unregister_media_controller(dev->m2m_dev_dec);
+error_m2m_mc_register:
+ media_device_cleanup(&dev->mdev);
+err_vid_dev_register:
+ v4l2_m2m_release(dev->m2m_dev_dec);
+err_hw_init:
+ dev->dec_hw = NULL;
+err_dec_mem_init:
+ video_device_release(vfd_dec);
+err_device_alloc:
+ v4l2_device_unregister(&dev->v4l2_dev);
+ return ret;
+}
+
+static void aml_vdec_drv_remove(struct platform_device *pdev)
+{
+ struct aml_vdec_dev *dev = platform_get_drvdata(pdev);
+
+ vdec_disable(dev->dec_hw);
+
+ if (media_devnode_is_registered(dev->mdev.devnode)) {
+ media_device_unregister(&dev->mdev);
+ media_device_cleanup(&dev->mdev);
+ }
+
+ if (dev->m2m_dev_dec)
+ v4l2_m2m_release(dev->m2m_dev_dec);
+ if (dev->vfd)
+ video_unregister_device(dev->vfd);
+ if (dev->dec_hw) {
I do not understand why do you release resources conditionally. Where
they allocated conditionally? Why probe is not releasing them the same
way in error paths?

These resources are allocated unconditionally in probe, so they should be released unconditionally as well.

I was being overly cautious here to avoid potential double-free scenarios. But in fact these resources are only released in remove(), so the conditional is redundant. I'll drop it in the next revision.


+ dev->pvdec_data->destroy_hw_resource(dev);
+ dev->dec_hw = NULL;
What's the purpose of this? If this is needed, then your driver has
serious concurrency issues which are not solved with it.

Do you mean the statement 'dev->dec_hw = NULL;'? Actuallyin the remove callback, all resources are at the end of their lifecycle and no other path will access this pointer. This was just my coding habit, nulling out pointers after freeing them. I'll drop it if you think this is unnecessary.
+ }
+ v4l2_device_unregister(&dev->v4l2_dev);
+}
+
+static const struct of_device_id aml_vdec_match[] = {
+ {.compatible = "amlogic,s4-vdec", .data = &aml_vdec_s4_pdata},
Fix the style, so you will not re-introduce issue Uwe is fixing.
Thanks for the reminder. I will refer to Uwe's patch and improve this.


Best regards,
Krzysztof

BRs

Zhentao