media: dmxdev: Fix the logic that enables DMA mmap support

Some conditions required for DVB mmap support to work are reversed.
Also, the logic is not too clear.

So, improve the logic, making it easier to be handled.

PS.: I'm pretty sure that I fixed it while testing, but, somehow,
the change got lost.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/dvb-core/dmxdev.c

@@ -128,11 +128,7 @@ static int dvb_dvr_open(struct inode *inode, struct file *file)
 	struct dvb_device *dvbdev = file->private_data;
 	struct dmxdev *dmxdev = dvbdev->priv;
 	struct dmx_frontend *front;
-#ifndef CONFIG_DVB_MMAP
 	bool need_ringbuffer = false;
-#else
-	const bool need_ringbuffer = true;
-#endif
 
 	dprintk("%s\n", __func__);
 
@@ -144,17 +140,31 @@ static int dvb_dvr_open(struct inode *inode, struct file *file)
 		return -ENODEV;
 	}
 
-#ifndef CONFIG_DVB_MMAP
+	dmxdev->may_do_mmap = 0;
+
+	/*
+	 * The logic here is a little tricky due to the ifdef.
+	 *
+	 * The ringbuffer is used for both read and mmap.
+	 *
+	 * It is not needed, however, on two situations:
+	 *	- Write devices (access with O_WRONLY);
+	 *	- For duplex device nodes, opened with O_RDWR.
+	 */
+
 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 		need_ringbuffer = true;
-#else
-	if ((file->f_flags & O_ACCMODE) == O_RDWR) {
+	else if ((file->f_flags & O_ACCMODE) == O_RDWR) {
 		if (!(dmxdev->capabilities & DMXDEV_CAP_DUPLEX)) {
+#ifdef CONFIG_DVB_MMAP
+			dmxdev->may_do_mmap = 1;
+			need_ringbuffer = true;
+#else
 			mutex_unlock(&dmxdev->mutex);
 			return -EOPNOTSUPP;
+#endif
 		}
 	}
-#endif
 
 	if (need_ringbuffer) {
 		void *mem;
@@ -169,8 +179,9 @@ static int dvb_dvr_open(struct inode *inode, struct file *file)
 			return -ENOMEM;
 		}
 		dvb_ringbuffer_init(&dmxdev->dvr_buffer, mem, DVR_BUFFER_SIZE);
-		dvb_vb2_init(&dmxdev->dvr_vb2_ctx, "dvr",
-			     file->f_flags & O_NONBLOCK);
+		if (dmxdev->may_do_mmap)
+			dvb_vb2_init(&dmxdev->dvr_vb2_ctx, "dvr",
+				     file->f_flags & O_NONBLOCK);
 		dvbdev->readers--;
 	}
 
@@ -200,11 +211,6 @@ static int dvb_dvr_release(struct inode *inode, struct file *file)
 {
 	struct dvb_device *dvbdev = file->private_data;
 	struct dmxdev *dmxdev = dvbdev->priv;
-#ifndef CONFIG_DVB_MMAP
-	bool need_ringbuffer = false;
-#else
-	const bool need_ringbuffer = true;
-#endif
 
 	mutex_lock(&dmxdev->mutex);
 
@@ -213,15 +219,14 @@ static int dvb_dvr_release(struct inode *inode, struct file *file)
 		dmxdev->demux->connect_frontend(dmxdev->demux,
 						dmxdev->dvr_orig_fe);
 	}
-#ifndef CONFIG_DVB_MMAP
-	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
-		need_ringbuffer = true;
-#endif
 
-	if (need_ringbuffer) {
-		if (dvb_vb2_is_streaming(&dmxdev->dvr_vb2_ctx))
-			dvb_vb2_stream_off(&dmxdev->dvr_vb2_ctx);
-		dvb_vb2_release(&dmxdev->dvr_vb2_ctx);
+	if (((file->f_flags & O_ACCMODE) == O_RDONLY) ||
+	    dmxdev->may_do_mmap) {
+		if (dmxdev->may_do_mmap) {
+			if (dvb_vb2_is_streaming(&dmxdev->dvr_vb2_ctx))
+				dvb_vb2_stream_off(&dmxdev->dvr_vb2_ctx);
+			dvb_vb2_release(&dmxdev->dvr_vb2_ctx);
+		}
 		dvbdev->readers++;
 		if (dmxdev->dvr_buffer.data) {
 			void *mem = dmxdev->dvr_buffer.data;
@@ -802,6 +807,12 @@ static int dvb_demux_open(struct inode *inode, struct file *file)
 	mutex_init(&dmxdevfilter->mutex);
 	file->private_data = dmxdevfilter;
 
+#ifdef CONFIG_DVB_MMAP
+	dmxdev->may_do_mmap = 1;
+#else
+	dmxdev->may_do_mmap = 0;
+#endif
+
 	dvb_ringbuffer_init(&dmxdevfilter->buffer, NULL, 8192);
 	dvb_vb2_init(&dmxdevfilter->vb2_ctx, "demux_filter",
 		     file->f_flags & O_NONBLOCK);
@@ -1206,6 +1217,9 @@ static int dvb_demux_mmap(struct file *file, struct vm_area_struct *vma)
 	struct dmxdev *dmxdev = dmxdevfilter->dev;
 	int ret;
 
+	if (!dmxdev->may_do_mmap)
+		return -EOPNOTSUPP;
+
 	if (mutex_lock_interruptible(&dmxdev->mutex))
 		return -ERESTARTSYS;
 
@@ -1322,11 +1336,6 @@ static __poll_t dvb_dvr_poll(struct file *file, poll_table *wait)
 	struct dvb_device *dvbdev = file->private_data;
 	struct dmxdev *dmxdev = dvbdev->priv;
 	__poll_t mask = 0;
-#ifndef CONFIG_DVB_MMAP
-	bool need_ringbuffer = false;
-#else
-	const bool need_ringbuffer = true;
-#endif
 
 	dprintk("%s\n", __func__);
 
@@ -1337,11 +1346,8 @@ static __poll_t dvb_dvr_poll(struct file *file, poll_table *wait)
 
 	poll_wait(file, &dmxdev->dvr_buffer.queue, wait);
 
-#ifndef CONFIG_DVB_MMAP
-	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
-		need_ringbuffer = true;
-#endif
-	if (need_ringbuffer) {
+	if (((file->f_flags & O_ACCMODE) == O_RDONLY) ||
+	    dmxdev->may_do_mmap) {
 		if (dmxdev->dvr_buffer.error)
 			mask |= (EPOLLIN | EPOLLRDNORM | EPOLLPRI | EPOLLERR);
 
@@ -1360,6 +1366,9 @@ static int dvb_dvr_mmap(struct file *file, struct vm_area_struct *vma)
 	struct dmxdev *dmxdev = dvbdev->priv;
 	int ret;
 
+	if (!dmxdev->may_do_mmap)
+		return -EOPNOTSUPP;
+
 	if (dmxdev->exit)
 		return -ENODEV;
 

include/media/dmxdev.h

@@ -163,6 +163,7 @@ struct dmxdev_filter {
  * @demux:		pointer to &struct dmx_demux.
  * @filternum:		number of filters.
  * @capabilities:	demux capabilities as defined by &enum dmx_demux_caps.
+ * @may_do_mmap:	flag used to indicate if the device may do mmap.
  * @exit:		flag to indicate that the demux is being released.
  * @dvr_orig_fe:	pointer to &struct dmx_frontend.
  * @dvr_buffer:		embedded &struct dvb_ringbuffer for DVB output.
@@ -180,6 +181,7 @@ struct dmxdev {
 	int filternum;
 	int capabilities;
 
+	unsigned int may_do_mmap:1;
 	unsigned int exit:1;
 #define DMXDEV_CAP_DUPLEX 1
 	struct dmx_frontend *dvr_orig_fe;