Re: [PATCH v3 1/2] media: vimc: Collapse component structure into a single monolithic driver

From: Shuah Khan
Date: Tue Aug 27 2019 - 14:17:10 EST

On 8/27/19 10:55 AM, Laurent Pinchart wrote:
Hi Shuah,

Thank you for the patch.

On Tue, Aug 20, 2019 at 03:18:41PM -0600, Shuah Khan wrote:
vimc uses Component API to split the driver into functional components.
The real hardware resembles a monolith structure than component and
component structure added a level of complexity making it hard to
maintain without adding any real benefit.

The sensor is one vimc component that would makes sense to be a separate
module to closely align with the real hardware. It would be easier to
collapse vimc into single monolithic driver first and then split the
sensor off as a separate module.

Collapse it into a single monolithic driver removing the Component API.
This patch removes the component API and makes minimal changes to the
code base preserving the functional division of the code structure.
Preserving the functional structure allows us to split the sensor off
as a separate module in the future.

Major design elements in this change are:
- Use existing struct vimc_ent_config and struct vimc_pipeline_config
to drive the initialization of the functional components.
- Make vimc_device and vimc_ent_config global by moving them to
vimc-common.h
- Add two new hooks add and rm to initialize and register, unregister
and free subdevs.
- All component API is now gone and bind and unbind hooks are modified
to do "add" and "rm" with minimal changes to just add and rm subdevs.
- vimc-core's bind and unbind are now register and unregister.
- vimc-core invokes "add" hooks from its vimc_register_devices().
The "add" hooks remain the same and register subdevs. They don't
create platform devices of their own and use vimc's pdev.dev as
their reference device. The "add" hooks save their vimc_ent_device(s)
in the corresponding vimc_ent_config.
- vimc-core invokes "rm" hooks from its unregister to unregister subdevs
and cleanup.
- vimc-core invokes "add" and "rm" hooks with pointer to struct vimc_device
and the corresponding struct vimc_ent_config pointer.

The following configure and stream test works on all devices.

media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]'
media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]'
media-ctl -d platform:vimc -V '"Sensor B":0[fmt:SBGGR8_1X8/640x480]'
media-ctl -d platform:vimc -V '"Debayer B":0[fmt:SBGGR8_1X8/640x480]'

v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=1920,height=1440
v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81
v4l2-ctl -z platform:vimc -d "Raw Capture 1" -v pixelformat=BA81

v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video1
v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video2
v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video3

Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
---
drivers/media/platform/vimc/Makefile | 7 +-
drivers/media/platform/vimc/vimc-capture.c | 79 ++------
drivers/media/platform/vimc/vimc-common.h | 48 +++++
drivers/media/platform/vimc/vimc-core.c | 199 ++++++++-------------
drivers/media/platform/vimc/vimc-debayer.c | 67 ++-----
drivers/media/platform/vimc/vimc-scaler.c | 71 ++------
drivers/media/platform/vimc/vimc-sensor.c | 71 ++------
7 files changed, 176 insertions(+), 366 deletions(-)

diff --git a/drivers/media/platform/vimc/Makefile b/drivers/media/platform/vimc/Makefile
index 96d06f030c31..a53b2b532e9f 100644
--- a/drivers/media/platform/vimc/Makefile
+++ b/drivers/media/platform/vimc/Makefile
@@ -1,5 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
-vimc-y := vimc-core.o vimc-common.o vimc-streamer.o
+vimc-y := vimc-core.o vimc-common.o vimc-streamer.o vimc-capture.o \
+ vimc-debayer.o vimc-scaler.o vimc-sensor.o
+
+obj-$(CONFIG_VIDEO_VIMC) += vimc.o
-obj-$(CONFIG_VIDEO_VIMC) += vimc.o vimc-capture.o vimc-debayer.o \
- vimc-scaler.o vimc-sensor.o
diff --git a/drivers/media/platform/vimc/vimc-capture.c b/drivers/media/platform/vimc/vimc-capture.c
index 1d56b91830ba..e04b60ec0738 100644
--- a/drivers/media/platform/vimc/vimc-capture.c
+++ b/drivers/media/platform/vimc/vimc-capture.c
@@ -5,10 +5,6 @@
* Copyright (C) 2015-2017 Helen Koike <helen.fornazier@xxxxxxxxx>
*/
-#include <linux/component.h>
-#include <linux/module.h>
-#include <linux/mod_devicetable.h>
-#include <linux/platform_device.h>
#include <media/v4l2-ioctl.h>
#include <media/videobuf2-core.h>
#include <media/videobuf2-vmalloc.h>
@@ -16,8 +12,6 @@
#include "vimc-common.h"
#include "vimc-streamer.h"
-#define VIMC_CAP_DRV_NAME "vimc-capture"
-
struct vimc_cap_device {
struct vimc_ent_device ved;
struct video_device vdev;
@@ -340,13 +334,15 @@ static void vimc_cap_release(struct video_device *vdev)
kfree(vcap);
}
-static void vimc_cap_comp_unbind(struct device *comp, struct device *master,
- void *master_data)
+void vimc_cap_rm(struct vimc_device *vimc, struct vimc_ent_config *vcfg)
{
- struct vimc_ent_device *ved = dev_get_drvdata(comp);
- struct vimc_cap_device *vcap = container_of(ved, struct vimc_cap_device,
- ved);
+ struct vimc_ent_device *ved = vcfg->ved;
+ struct vimc_cap_device *vcap;
+
+ if (!ved)
+ return;
+ vcap = container_of(ved, struct vimc_cap_device, ved);
vb2_queue_release(&vcap->queue);
media_entity_cleanup(ved->ent);
video_unregister_device(&vcap->vdev);
@@ -391,11 +387,9 @@ static void *vimc_cap_process_frame(struct vimc_ent_device *ved,
return NULL;
}
-static int vimc_cap_comp_bind(struct device *comp, struct device *master,
- void *master_data)
+int vimc_cap_add(struct vimc_device *vimc, struct vimc_ent_config *vcfg)
{
- struct v4l2_device *v4l2_dev = master_data;
- struct vimc_platform_data *pdata = comp->platform_data;
+ struct v4l2_device *v4l2_dev = &vimc->v4l2_dev;
const struct vimc_pix_map *vpix;
struct vimc_cap_device *vcap;
struct video_device *vdev;
@@ -416,7 +410,7 @@ static int vimc_cap_comp_bind(struct device *comp, struct device *master,
}
/* Initialize the media entity */
- vcap->vdev.entity.name = pdata->entity_name;
+ vcap->vdev.entity.name = vcfg->name;
vcap->vdev.entity.function = MEDIA_ENT_F_IO_V4L;
ret = media_entity_pads_init(&vcap->vdev.entity,
1, vcap->ved.pads);
@@ -440,8 +434,8 @@ static int vimc_cap_comp_bind(struct device *comp, struct device *master,
ret = vb2_queue_init(q);
if (ret) {
- dev_err(comp, "%s: vb2 queue init failed (err=%d)\n",
- pdata->entity_name, ret);
+ dev_err(&vimc->pdev.dev, "%s: vb2 queue init failed (err=%d)\n",
+ vcfg->name, ret);
goto err_clean_m_ent;
}
@@ -460,8 +454,7 @@ static int vimc_cap_comp_bind(struct device *comp, struct device *master,
vcap->ved.ent = &vcap->vdev.entity;
vcap->ved.process_frame = vimc_cap_process_frame;
vcap->ved.vdev_get_format = vimc_cap_get_format;
- dev_set_drvdata(comp, &vcap->ved);
- vcap->dev = comp;
+ vcap->dev = &vimc->pdev.dev;
/* Initialize the video_device struct */
vdev = &vcap->vdev;
@@ -474,17 +467,18 @@ static int vimc_cap_comp_bind(struct device *comp, struct device *master,
vdev->queue = q;
vdev->v4l2_dev = v4l2_dev;
vdev->vfl_dir = VFL_DIR_RX;
- strscpy(vdev->name, pdata->entity_name, sizeof(vdev->name));
+ strscpy(vdev->name, vcfg->name, sizeof(vdev->name));
video_set_drvdata(vdev, &vcap->ved);
/* Register the video_device with the v4l2 and the media framework */
ret = video_register_device(vdev, VFL_TYPE_GRABBER, -1);
if (ret) {
- dev_err(comp, "%s: video register failed (err=%d)\n",
+ dev_err(&vimc->pdev.dev, "%s: video register failed (err=%d)\n",
vcap->vdev.name, ret);
goto err_release_queue;
}
+ vcfg->ved = &vcap->ved;
return 0;
err_release_queue:
@@ -498,44 +492,3 @@ static int vimc_cap_comp_bind(struct device *comp, struct device *master,
return ret;
}
-
-static const struct component_ops vimc_cap_comp_ops = {
- .bind = vimc_cap_comp_bind,
- .unbind = vimc_cap_comp_unbind,
-};
-
-static int vimc_cap_probe(struct platform_device *pdev)
-{
- return component_add(&pdev->dev, &vimc_cap_comp_ops);
-}
-
-static int vimc_cap_remove(struct platform_device *pdev)
-{
- component_del(&pdev->dev, &vimc_cap_comp_ops);
-
- return 0;
-}
-
-static const struct platform_device_id vimc_cap_driver_ids[] = {
- {
- .name = VIMC_CAP_DRV_NAME,
- },
- { }
-};
-
-static struct platform_driver vimc_cap_pdrv = {
- .probe = vimc_cap_probe,
- .remove = vimc_cap_remove,
- .id_table = vimc_cap_driver_ids,
- .driver = {
- .name = VIMC_CAP_DRV_NAME,
- },
-};
-
-module_platform_driver(vimc_cap_pdrv);
-
-MODULE_DEVICE_TABLE(platform, vimc_cap_driver_ids);
-
-MODULE_DESCRIPTION("Virtual Media Controller Driver (VIMC) Capture");
-MODULE_AUTHOR("Helen Mae Koike Fornazier <helen.fornazier@xxxxxxxxx>");
-MODULE_LICENSE("GPL");
diff --git a/drivers/media/platform/vimc/vimc-common.h b/drivers/media/platform/vimc/vimc-common.h
index 9c2e0e216c6b..5b2282de395c 100644
--- a/drivers/media/platform/vimc/vimc-common.h
+++ b/drivers/media/platform/vimc/vimc-common.h
@@ -9,6 +9,7 @@
#define _VIMC_COMMON_H_
#include <linux/slab.h>
+#include <linux/platform_device.h>
#include <media/media-device.h>
#include <media/v4l2-device.h>
@@ -84,6 +85,21 @@ struct vimc_pix_map {
bool bayer;
};
+/**
+ * struct vimc_device - main device for vimc driver
+ *
+ * @pdev pointer to the platform device
+ * @pipe_cfg pointer to the vimc pipeline configuration structure
+ * @mdev the associated media_device parent
+ * @v4l2_dev Internal v4l2 parent device
+ */
+struct vimc_device {
+ struct platform_device pdev;
+ const struct vimc_pipeline_config *pipe_cfg;
+ struct media_device mdev;
+ struct v4l2_device v4l2_dev;
+};
+
/**
* struct vimc_ent_device - core struct that represents a node in the topology
*
@@ -111,6 +127,38 @@ struct vimc_ent_device {
struct v4l2_pix_format *fmt);
};
+/**
+ * struct vimc_ent_config Structure which describes individual
+ * configuration for each entity
+ *
+ * @name entity name
+ * @ved pointer to vimc_ent_device (a node in the
+ * topology)
+ * @add subdev add hook - initializes and registers
+ * subdev called from vimc-core
+ * @rm subdev rm hook - unregisters and frees
+ * subdev called from vimc-core
+ */
+struct vimc_ent_config {
+ const char *name;
+ struct vimc_ent_device *ved;
+ int (*add)(struct vimc_device *vimc, struct vimc_ent_config *vcfg);
+ void (*rm)(struct vimc_device *vimc, struct vimc_ent_config *vcfg);
+};

Mixing data and function pointers in a read-write structure is a
security issue, as it helps an attacker who could overwrite the
structure to run arbitrary code :-/ I think you should split this in
two, with the read-only name and function pointers stored as a const
array, and the vimc_ent_device pointers stored separately (possibly in a
linked list, or worst case an array that mirrors ent_config, as I
suppose the configfs support will remove the ent_config array).


Array that mirrors might be sufficient. We do all or nothing adds for
these entities anyway. If we can't add one entity, we delete all and
fail the probe.

This is I think the only blocker for this patch series, and fortunately
it shouldn't be difficult to fix.


Yeah. I should have thought about that in the first place. :( Will fix
it and send updated patch.

thanks,
-- Shuah