ALSA CVS update - Takashi Iwai <tiwai@suse.de>

CS4231 driver
checks the PCM substream pointers to fix oops/panic in the interrupt
handler.

sound/isa/cs423x/cs4231_lib.c

@@ -979,21 +979,28 @@ irqreturn_t snd_cs4231_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 	}		
 	if (chip->single_dma && chip->hardware != CS4231_HW_INTERWAVE) {
 		if (status & CS4231_PLAYBACK_IRQ) {
-			if (chip->mode & CS4231_MODE_PLAY)
+			if (chip->mode & CS4231_MODE_PLAY) {
+				if (chip->playback_substream)
 					snd_pcm_period_elapsed(chip->playback_substream);
+			}
 			if (chip->mode & CS4231_MODE_RECORD) {
+				if (chip->capture_substream) {
 					snd_cs4231_overrange(chip);
 					snd_pcm_period_elapsed(chip->capture_substream);
 				}
 			}
+		}
 	} else {
-		if (status & CS4231_PLAYBACK_IRQ)
+		if (status & CS4231_PLAYBACK_IRQ) {
+			if (chip->playback_substream)
 				snd_pcm_period_elapsed(chip->playback_substream);
 		if (status & CS4231_RECORD_IRQ) {
+			if (chip->capture_substream) {
 				snd_cs4231_overrange(chip);
 				snd_pcm_period_elapsed(chip->capture_substream);
 			}
 		}
+	}
 
 	spin_lock(&chip->reg_lock);
 	snd_cs4231_outm(chip, CS4231_IRQ_STATUS, ~CS4231_ALL_IRQS | ~status, 0);