V4L/DVB (10083): soc-camera: unify locking, play nicer with videobuf locking

Move mutex from host drivers to camera device object, take into account
videobuf locking.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

3 files changed, 91 insertions, 32 deletions

diff --git a/drivers/media/video/pxa_camera.c b/drivers/media/video/pxa_camera.c
index aa7efc45d364..c3c50de0aa50 100644
--- a/drivers/media/video/pxa_camera.c
+++ b/drivers/media/video/pxa_camera.c
@@ -25,7 +25,6 @@
 #include <linux/version.h>
 #include <linux/device.h>
 #include <linux/platform_device.h>
-#include <linux/mutex.h>
 #include <linux/clk.h>
 
 #include <media/v4l2-common.h>
@@ -164,8 +163,6 @@
                         CICR0_PERRM | CICR0_QDM | CICR0_CDM | CICR0_SOFM | \
                         CICR0_EOFM | CICR0_FOM)
 
-static DEFINE_MUTEX(camera_lock);
-
 /*
  * Structures
  */
@@ -813,16 +810,17 @@ static irqreturn_t pxa_camera_irq(int irq, void *data)
         return IRQ_HANDLED;
 }
 
-/* The following two functions absolutely depend on the fact, that
- * there can be only one camera on PXA quick capture interface */
+/*
+ * The following two functions absolutely depend on the fact, that
+ * there can be only one camera on PXA quick capture interface
+ * Called with .video_lock held
+ */
 static int pxa_camera_add_device(struct soc_camera_device *icd)
 {
         struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
         struct pxa_camera_dev *pcdev = ici->priv;
         int ret;
 
-        mutex_lock(&camera_lock);
-
         if (pcdev->icd) {
                 ret = -EBUSY;
                 goto ebusy;
@@ -838,11 +836,10 @@ static int pxa_camera_add_device(struct soc_camera_device *icd)
                 pcdev->icd = icd;
 
 ebusy:
-        mutex_unlock(&camera_lock);
-
         return ret;
 }
 
+/* Called with .video_lock held */
 static void pxa_camera_remove_device(struct soc_camera_device *icd)
 {
         struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
diff --git a/drivers/media/video/sh_mobile_ceu_camera.c b/drivers/media/video/sh_mobile_ceu_camera.c
index a49bec1509f4..47ffa441c869 100644
--- a/drivers/media/video/sh_mobile_ceu_camera.c
+++ b/drivers/media/video/sh_mobile_ceu_camera.c
@@ -29,7 +29,6 @@
 #include <linux/version.h>
 #include <linux/device.h>
 #include <linux/platform_device.h>
-#include <linux/mutex.h>
 #include <linux/videodev2.h>
 #include <linux/clk.h>
 
@@ -75,8 +74,6 @@
 #define CDBYR2 0x98 /* Capture data bottom-field address Y register 2 */
 #define CDBCR2 0x9c /* Capture data bottom-field address C register 2 */
 
-static DEFINE_MUTEX(camera_lock);
-
 /* per video frame buffer */
 struct sh_mobile_ceu_buffer {
         struct videobuf_buffer vb; /* v4l buffer must be first */
@@ -292,14 +289,13 @@ static irqreturn_t sh_mobile_ceu_irq(int irq, void *data)
         return IRQ_HANDLED;
 }
 
+/* Called with .video_lock held */
 static int sh_mobile_ceu_add_device(struct soc_camera_device *icd)
 {
         struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
         struct sh_mobile_ceu_dev *pcdev = ici->priv;
         int ret = -EBUSY;
 
-        mutex_lock(&camera_lock);
-
         if (pcdev->icd)
                 goto err;
 
@@ -319,11 +315,10 @@ static int sh_mobile_ceu_add_device(struct soc_camera_device *icd)
 
         pcdev->icd = icd;
 err:
-        mutex_unlock(&camera_lock);
-
         return ret;
 }
 
+/* Called with .video_lock held */
 static void sh_mobile_ceu_remove_device(struct soc_camera_device *icd)
 {
         struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
diff --git a/drivers/media/video/soc_camera.c b/drivers/media/video/soc_camera.c
index d5613cdd93a6..e869670dbae5 100644
--- a/drivers/media/video/soc_camera.c
+++ b/drivers/media/video/soc_camera.c
@@ -33,7 +33,6 @@
 static LIST_HEAD(hosts);
 static LIST_HEAD(devices);
 static DEFINE_MUTEX(list_lock);
-static DEFINE_MUTEX(video_lock);
 
 const struct soc_camera_data_format *soc_camera_format_by_fourcc(
         struct soc_camera_device *icd, unsigned int fourcc)
@@ -270,8 +269,10 @@ static int soc_camera_open(struct inode *inode, struct file *file)
         if (!icf)
                 return -ENOMEM;
 
-        /* Protect against icd->remove() until we module_get() both drivers. */
-        mutex_lock(&video_lock);
+        /*
+         * It is safe to dereference these pointers now as long as a user has
+         * the video device open - we are protected by the held cdev reference.
+         */
 
         vdev = video_devdata(file);
         icd = container_of(vdev->parent, struct soc_camera_device, dev);
@@ -289,6 +290,9 @@ static int soc_camera_open(struct inode *inode, struct file *file)
                 goto emgi;
         }
 
+        /* Protect against icd->remove() until we module_get() both drivers. */
+        mutex_lock(&icd->video_lock);
+
         icf->icd = icd;
         icd->use_count++;
 
@@ -304,7 +308,7 @@ static int soc_camera_open(struct inode *inode, struct file *file)
                 }
         }
 
-        mutex_unlock(&video_lock);
+        mutex_unlock(&icd->video_lock);
 
         file->private_data = icf;
         dev_dbg(&icd->dev, "camera device open\n");
@@ -313,16 +317,16 @@ static int soc_camera_open(struct inode *inode, struct file *file)
 
         return 0;
 
-        /* All errors are entered with the video_lock held */
+        /* First two errors are entered with the .video_lock held */
 eiciadd:
         soc_camera_free_user_formats(icd);
 eiufmt:
         icd->use_count--;
+        mutex_unlock(&icd->video_lock);
         module_put(ici->ops->owner);
 emgi:
         module_put(icd->ops->owner);
 emgd:
-        mutex_unlock(&video_lock);
         vfree(icf);
         return ret;
 }
@@ -334,15 +338,16 @@ static int soc_camera_close(struct inode *inode, struct file *file)
         struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
         struct video_device *vdev = icd->vdev;
 
-        mutex_lock(&video_lock);
+        mutex_lock(&icd->video_lock);
         icd->use_count--;
         if (!icd->use_count) {
                 ici->ops->remove(icd);
                 soc_camera_free_user_formats(icd);
         }
+        mutex_unlock(&icd->video_lock);
+
         module_put(icd->ops->owner);
         module_put(ici->ops->owner);
-        mutex_unlock(&video_lock);
 
         vfree(icf);
 
@@ -424,18 +429,27 @@ static int soc_camera_s_fmt_vid_cap(struct file *file, void *priv,
         if (ret < 0)
                 return ret;
 
+        mutex_lock(&icf->vb_vidq.vb_lock);
+
+        if (videobuf_queue_is_busy(&icf->vb_vidq)) {
+                dev_err(&icd->dev, "S_FMT denied: queue busy\n");
+                ret = -EBUSY;
+                goto unlock;
+        }
+
         rect.left       = icd->x_current;
         rect.top        = icd->y_current;
         rect.width      = pix->width;
         rect.height     = pix->height;
         ret = ici->ops->set_fmt(icd, pix->pixelformat, &rect);
         if (ret < 0) {
-                return ret;
+                goto unlock;
         } else if (!icd->current_fmt ||
                    icd->current_fmt->fourcc != pixfmt) {
                 dev_err(&ici->dev,
                         "Host driver hasn't set up current format correctly!\n");
-                return -EINVAL;
+                ret = -EINVAL;
+                goto unlock;
         }
 
         icd->width              = rect.width;
@@ -449,7 +463,12 @@ static int soc_camera_s_fmt_vid_cap(struct file *file, void *priv,
                 icd->width, icd->height);
 
         /* set physical bus parameters */
-        return ici->ops->set_bus_param(icd, pixfmt);
+        ret = ici->ops->set_bus_param(icd, pixfmt);
+
+unlock:
+        mutex_unlock(&icf->vb_vidq.vb_lock);
+
+        return ret;
 }
 
 static int soc_camera_enum_fmt_vid_cap(struct file *file, void  *priv,
@@ -510,6 +529,7 @@ static int soc_camera_streamon(struct file *file, void *priv,
 {
         struct soc_camera_file *icf = file->private_data;
         struct soc_camera_device *icd = icf->icd;
+        int ret;
 
         WARN_ON(priv != file->private_data);
 
@@ -518,10 +538,16 @@ static int soc_camera_streamon(struct file *file, void *priv,
         if (i != V4L2_BUF_TYPE_VIDEO_CAPTURE)
                 return -EINVAL;
 
+        mutex_lock(&icd->video_lock);
+
         icd->ops->start_capture(icd);
 
         /* This calls buf_queue from host driver's videobuf_queue_ops */
-        return videobuf_streamon(&icf->vb_vidq);
+        ret = videobuf_streamon(&icf->vb_vidq);
+
+        mutex_unlock(&icd->video_lock);
+
+        return ret;
 }
 
 static int soc_camera_streamoff(struct file *file, void *priv,
@@ -537,12 +563,16 @@ static int soc_camera_streamoff(struct file *file, void *priv,
         if (i != V4L2_BUF_TYPE_VIDEO_CAPTURE)
                 return -EINVAL;
 
+        mutex_lock(&icd->video_lock);
+
         /* This calls buf_release from host driver's videobuf_queue_ops for all
          * remaining buffers. When the last buffer is freed, stop capture */
         videobuf_streamoff(&icf->vb_vidq);
 
         icd->ops->stop_capture(icd);
 
+        mutex_unlock(&icd->video_lock);
+
         return 0;
 }
 
@@ -654,6 +684,9 @@ static int soc_camera_s_crop(struct file *file, void *fh,
         if (a->type != V4L2_BUF_TYPE_VIDEO_CAPTURE)
                 return -EINVAL;
 
+        /* Cropping is allowed during a running capture, guard consistency */
+        mutex_lock(&icf->vb_vidq.vb_lock);
+
         ret = ici->ops->set_fmt(icd, 0, &a->c);
         if (!ret) {
                 icd->width      = a->c.width;
@@ -662,6 +695,8 @@ static int soc_camera_s_crop(struct file *file, void *fh,
                 icd->y_current  = a->c.top;
         }
 
+        mutex_unlock(&icf->vb_vidq.vb_lock);
+
         return ret;
 }
 
@@ -775,11 +810,32 @@ static int soc_camera_probe(struct device *dev)
         struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
         int ret;
 
+        /*
+         * Possible race scenario:
+         * modprobe <camera-host-driver> triggers __func__
+         * at this moment respective <camera-sensor-driver> gets rmmod'ed
+         * to protect take module references.
+         */
+
+        if (!try_module_get(icd->ops->owner)) {
+                dev_err(&icd->dev, "Couldn't lock sensor driver.\n");
+                ret = -EINVAL;
+                goto emgd;
+        }
+
+        if (!try_module_get(ici->ops->owner)) {
+                dev_err(&icd->dev, "Couldn't lock capture bus driver.\n");
+                ret = -EINVAL;
+                goto emgi;
+        }
+
+        mutex_lock(&icd->video_lock);
+
         /* We only call ->add() here to activate and probe the camera.
          * We shall ->remove() and deactivate it immediately afterwards. */
         ret = ici->ops->add(icd);
         if (ret < 0)
-                return ret;
+                goto eiadd;
 
         ret = icd->ops->probe(icd);
         if (ret >= 0) {
@@ -793,6 +849,12 @@ static int soc_camera_probe(struct device *dev)
         }
         ici->ops->remove(icd);
 
+eiadd:
+        mutex_unlock(&icd->video_lock);
+        module_put(ici->ops->owner);
+emgi:
+        module_put(icd->ops->owner);
+emgd:
         return ret;
 }
 
@@ -966,6 +1028,7 @@ int soc_camera_device_register(struct soc_camera_device *icd)
         icd->dev.release        = dummy_release;
         icd->use_count          = 0;
         icd->host_priv          = NULL;
+        mutex_init(&icd->video_lock);
 
         return scan_add_device(icd);
 }
@@ -1012,6 +1075,10 @@ static const struct v4l2_ioctl_ops soc_camera_ioctl_ops = {
 #endif
 };
 
+/*
+ * Usually called from the struct soc_camera_ops .probe() method, i.e., from
+ * soc_camera_probe() above with .video_lock held
+ */
 int soc_camera_video_start(struct soc_camera_device *icd)
 {
         struct soc_camera_host *ici = to_soc_camera_host(icd->dev.parent);
@@ -1027,7 +1094,7 @@ int soc_camera_video_start(struct soc_camera_device *icd)
         dev_dbg(&ici->dev, "Allocated video_device %p\n", vdev);
 
         strlcpy(vdev->name, ici->drv_name, sizeof(vdev->name));
-        /* Maybe better &ici->dev */
+
         vdev->parent            = &icd->dev;
         vdev->current_norm      = V4L2_STD_UNKNOWN;
         vdev->fops              = &soc_camera_fops;
@@ -1061,10 +1128,10 @@ void soc_camera_video_stop(struct soc_camera_device *icd)
         if (!icd->dev.parent || !vdev)
                 return;
 
-        mutex_lock(&video_lock);
+        mutex_lock(&icd->video_lock);
         video_unregister_device(vdev);
         icd->vdev = NULL;
-        mutex_unlock(&video_lock);
+        mutex_unlock(&icd->video_lock);
 }
 EXPORT_SYMBOL(soc_camera_video_stop);