[media] pwc: Avoid unnecessarily rebuilding the decoder tables

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/pwc/pwc-dec23.c

@@ -301,6 +301,9 @@ void pwc_dec23_init(struct pwc_device *pdev, unsigned char *cmd)
 
 	mutex_init(&pdec->lock);
 
+	if (pdec->last_cmd_valid && pdec->last_cmd == cmd[2])
+		return;
+
 	if (DEVICE_USE_CODEC3(pdev->type)) {
 		flags = cmd[2] & 0x18;
 		if (flags == 8)
@@ -347,6 +350,9 @@ void pwc_dec23_init(struct pwc_device *pdev, unsigned char *cmd)
 	for (i=0; i<MAX_OUTER_CROP_VALUE; i++)
 		pwc_crop_table[MAX_OUTER_CROP_VALUE+256+i] = 255;
 #endif
+
+	pdec->last_cmd = cmd[2];
+	pdec->last_cmd_valid = 1;
 }
 
 /*

drivers/media/video/pwc/pwc-dec23.h

@@ -31,11 +31,14 @@ struct pwc_dec23_private
 {
 	struct mutex lock;
 
+	unsigned char last_cmd, last_cmd_valid;
+
   unsigned int scalebits;
   unsigned int nbitsmask, nbits; /* Number of bits of a color in the compressed stream */
 
   unsigned int reservoir;
   unsigned int nbits_in_reservoir;
+
   const unsigned char *stream;
   int temp_colors[16];