[sound/oss i810] fix partial DMA transfers

This patch fixes a longstanding bug in this driver where partial fragments
are fed to the hardware.  Worse yet, those fragments are then extended
while the hardware is doing DMA transfers causing all sorts of problems.

sound/oss/i810_audio.c

@@ -1080,31 +1080,41 @@ static void __i810_update_lvi(struct i810_state *state, int rec)
 {
 	struct dmabuf *dmabuf = &state->dmabuf;
 	int x, port;
+	int trigger;
+	int count, fragsize;
+	void (*start)(struct i810_state *);
 
+	count = dmabuf->count;
 	port = state->card->iobase;
-	if(rec)
+	if (rec) {
 		port += dmabuf->read_channel->port;
-	else
+		trigger = PCM_ENABLE_INPUT;
+		start = __start_adc;
+		count = dmabuf->dmasize - count;
+	} else {
 		port += dmabuf->write_channel->port;
+		trigger = PCM_ENABLE_OUTPUT;
+		start = __start_dac;
+	}
+
+	/* Do not process partial fragments. */
+	fragsize = dmabuf->fragsize;
+	if (count < fragsize)
+		return;
 
 	if (!dmabuf->enable && dmabuf->ready) {
-		if(rec && dmabuf->count < dmabuf->dmasize &&
-		   (dmabuf->trigger & PCM_ENABLE_INPUT))
-		{
-			__start_adc(state);
-			while( !(inb(port + OFF_CR) & ((1<<4) | (1<<2))) ) ;
-		} else if (!rec && dmabuf->count &&
-			   (dmabuf->trigger & PCM_ENABLE_OUTPUT))
-		{
-			__start_dac(state);
-			while( !(inb(port + OFF_CR) & ((1<<4) | (1<<2))) ) ;
-		}
+		if (!(dmabuf->trigger & trigger))
+			return;
+
+		start(state);
+		while (!(inb(port + OFF_CR) & ((1<<4) | (1<<2))))
+			;
 	}
 
-	/* swptr - 1 is the tail of our transfer */
-	x = (dmabuf->dmasize + dmabuf->swptr - 1) % dmabuf->dmasize;
-	x /= dmabuf->fragsize;
-	outb(x, port+OFF_LVI);
+	/* MASKP2(swptr, fragsize) - 1 is the tail of our transfer */
+	x = MODULOP2(MASKP2(dmabuf->swptr, fragsize) - 1, dmabuf->dmasize);
+	x /= fragsize;
+	outb(x, port + OFF_LVI);
 }
 
 static void i810_update_lvi(struct i810_state *state, int rec)
@@ -1124,13 +1134,17 @@ static void i810_update_ptr(struct i810_state *state)
 {
 	struct dmabuf *dmabuf = &state->dmabuf;
 	unsigned hwptr;
+	unsigned fragmask, dmamask;
 	int diff;
 
-	/* error handling and process wake up for DAC */
+	fragmask = MASKP2(~0, dmabuf->fragsize);
+	dmamask = MODULOP2(~0, dmabuf->dmasize);
+
+	/* error handling and process wake up for ADC */
 	if (dmabuf->enable == ADC_RUNNING) {
 		/* update hardware pointer */
-		hwptr = i810_get_dma_addr(state, 1);
-		diff = (dmabuf->dmasize + hwptr - dmabuf->hwptr) % dmabuf->dmasize;
+		hwptr = i810_get_dma_addr(state, 1) & fragmask;
+		diff = (hwptr - dmabuf->hwptr) & dmamask;
 #if defined(DEBUG_INTERRUPTS) || defined(DEBUG_MMAP)
 		printk("ADC HWP %d,%d,%d\n", hwptr, dmabuf->hwptr, diff);
 #endif
@@ -1148,14 +1162,14 @@ static void i810_update_ptr(struct i810_state *state)
 				dmabuf->error++;
 			}
 		}
-		if (dmabuf->count > dmabuf->userfragsize)
+		if (diff)
 			wake_up(&dmabuf->wait);
 	}
 	/* error handling and process wake up for DAC */
 	if (dmabuf->enable == DAC_RUNNING) {
 		/* update hardware pointer */
-		hwptr = i810_get_dma_addr(state, 0);
-		diff = (dmabuf->dmasize + hwptr - dmabuf->hwptr) % dmabuf->dmasize;
+		hwptr = i810_get_dma_addr(state, 0) & fragmask;
+		diff = (hwptr - dmabuf->hwptr) & dmamask;
 #if defined(DEBUG_INTERRUPTS) || defined(DEBUG_MMAP)
 		printk("DAC HWP %d,%d,%d\n", hwptr, dmabuf->hwptr, diff);
 #endif
@@ -1178,7 +1192,7 @@ static void i810_update_ptr(struct i810_state *state)
 				dmabuf->error++;
 			}
 		}
-		if (dmabuf->count < (dmabuf->dmasize-dmabuf->userfragsize))
+		if (diff)
 			wake_up(&dmabuf->wait);
 	}
 }
@@ -1195,7 +1209,6 @@ static inline int i810_get_free_write_space(struct i810_state *state)
 		dmabuf->swptr = dmabuf->hwptr;
 	}
 	free = dmabuf->dmasize - dmabuf->count;
-	free -= (dmabuf->hwptr % dmabuf->fragsize);
 	if(free < 0)
 		return(0);
 	return(free);
@@ -1213,12 +1226,27 @@ static inline int i810_get_available_read_data(struct i810_state *state)
 		dmabuf->swptr = dmabuf->hwptr;
 	}
 	avail = dmabuf->count;
-	avail -= (dmabuf->hwptr % dmabuf->fragsize);
 	if(avail < 0)
 		return(0);
 	return(avail);
 }
 
+static inline void fill_partial_frag(struct dmabuf *dmabuf)
+{
+	unsigned fragsize;
+	unsigned swptr, len;
+
+	fragsize = dmabuf->fragsize;
+	swptr = dmabuf->swptr;
+	len = fragsize - MODULOP2(dmabuf->swptr, fragsize);
+	if (len == fragsize)
+		return;
+
+	memset(dmabuf->rawbuf + swptr, '\0', len);
+	dmabuf->swptr = MODULOP2(swptr + len, dmabuf->dmasize);
+	dmabuf->count += len;
+}
+
 static int drain_dac(struct i810_state *state, int signals_allowed)
 {
 	DECLARE_WAITQUEUE(wait, current);
@@ -1233,6 +1261,22 @@ static int drain_dac(struct i810_state *state, int signals_allowed)
 		stop_dac(state);
 		return 0;
 	}
+
+	spin_lock_irqsave(&state->card->lock, flags);
+
+	fill_partial_frag(dmabuf);
+
+	/* 
+	 * This will make sure that our LVI is correct, that our
+	 * pointer is updated, and that the DAC is running.  We
+	 * have to force the setting of dmabuf->trigger to avoid
+	 * any possible deadlocks.
+	 */
+	dmabuf->trigger = PCM_ENABLE_OUTPUT;
+	i810_update_lvi(state, 0);
+
+	spin_unlock_irqrestore(&state->card->lock, flags);
+
 	add_wait_queue(&dmabuf->wait, &wait);
 	for (;;) {
 
@@ -1255,16 +1299,6 @@ static int drain_dac(struct i810_state *state, int signals_allowed)
 		if (count <= 0)
 			break;
 
-		/* 
-		 * This will make sure that our LVI is correct, that our
-		 * pointer is updated, and that the DAC is running.  We
-		 * have to force the setting of dmabuf->trigger to avoid
-		 * any possible deadlocks.
-		 */
-		if(!dmabuf->enable) {
-			dmabuf->trigger = PCM_ENABLE_OUTPUT;
-			i810_update_lvi(state,0);
-		}
                 if (signal_pending(current) && signals_allowed) {
                         break;
                 }
@@ -1349,11 +1383,10 @@ static void i810_channel_interrupt(struct i810_card *card)
 			if(status & DMA_INT_DCH)
 				printk("DCH -");
 #endif
-			if(dmabuf->enable & DAC_RUNNING)
 			count = dmabuf->count;
-			else
-				count = dmabuf->dmasize - dmabuf->count;
-			if(count > 0) {
+			if(dmabuf->enable & ADC_RUNNING)
+				count = dmabuf->dmasize - count;
+			if (count >= (int)dmabuf->fragsize) {
 				outb(inb(port+OFF_CR) | 1, port+OFF_CR);
 #ifdef DEBUG_INTERRUPTS
 				printk(" CONTINUE ");
@@ -1525,7 +1558,7 @@ static ssize_t i810_read(struct file *file, char *buffer, size_t count, loff_t *
 			goto done;
 		}
 
-		swptr = (swptr + cnt) % dmabuf->dmasize;
+		swptr = MODULOP2(swptr + cnt, dmabuf->dmasize);
 
 		spin_lock_irqsave(&card->lock, flags);
 
@@ -1559,7 +1592,7 @@ static ssize_t i810_write(struct file *file, const char *buffer, size_t count, l
 	ssize_t ret;
 	unsigned long flags;
 	unsigned int swptr = 0;
-	int cnt, x;
+	int cnt;
         DECLARE_WAITQUEUE(waita, current);
 
 #ifdef DEBUG2
@@ -1683,10 +1716,6 @@ static ssize_t i810_write(struct file *file, const char *buffer, size_t count, l
 		ret += cnt;
 		spin_unlock_irqrestore(&state->card->lock, flags);
 	}
-	if (swptr % dmabuf->fragsize) {
-		x = dmabuf->fragsize - (swptr % dmabuf->fragsize);
-		memset(dmabuf->rawbuf + swptr, '\0', x);
-	}
 ret:
 	i810_update_lvi(state,0);
         set_current_state(TASK_RUNNING);