[PATCH] [UBUNTU:sound/drivers/mpu401/] Properly propagate error for nonexistent mpu401 interface

[crimsun at fungus.sh.nu]

Subject: [PATCH] [UBUNTU:sound/drivers/mpu401/] Properly propagate error for nonexistent mpu401 interface

UpstreamStatus: Added in http://hg-mirror.alsa-project.org/alsa-kernel?cmd=changeset;node=0209fc5b143c;style=gitweb

The following commit by Takashi Iwai fixes a hard freeze when
attempting to access a nonexistent mpu401 interface. Relevant portions
from this patch will be ported to the remaining sequencer files (see
Malone #34831).

sound: fix hang in mpu401_uart.c
Patch-level: Merged

This fixes a hang in mpu401_uart.c that can occur when the mpu401 interface
is non-existent or otherwise doesn't respond to commands but we issue IO
anyway. snd_mpu401_uart_cmd now returns an error code that is passed up
the stack so that an open() will fail immediately in such cases.

Eventually discovered after wine/cxoffice would constantly cause hard
lockups on my desktop immediately after loading (emulating Windows too
well). Turned out that I'd recently moved my sound cards around and using
/dev/sequencer now talks to a sound card with a broken MPU.

This second version changes -EFAULT to -EIO and frees open resources on
error too. Test booted and seems to work ok.

Signed-off-by: Daniel T Chen <crimsun at ubuntu.com>
Signed-off-by: Jon Masters <jcm at jonmasters.org>

---

 sound/drivers/mpu401/mpu401_uart.c |   40 ++++++++++++++++++++++++++++--------
 1 files changed, 31 insertions(+), 9 deletions(-)

01a9c0bd0e7bdce9972bc69c3e1503f06792d1ee
diff --git a/sound/drivers/mpu401/mpu401_uart.c b/sound/drivers/mpu401/mpu401_uart.c
index bdeb2c0..d6598b5 100644
--- a/sound/drivers/mpu401/mpu401_uart.c
+++ b/sound/drivers/mpu401/mpu401_uart.c
@@ -182,7 +182,7 @@ static void snd_mpu401_uart_remove_timer
 
  */
 
-static void snd_mpu401_uart_cmd(mpu401_t * mpu, unsigned char cmd, int ack)
+static int snd_mpu401_uart_cmd(mpu401_t * mpu, unsigned char cmd, int ack)
 {
 	unsigned long flags;
 	int timeout, ok;
@@ -217,9 +217,11 @@ static void snd_mpu401_uart_cmd(mpu401_t
 		ok = 1;
 	}
 	spin_unlock_irqrestore(&mpu->input_lock, flags);
-	if (! ok)
+	if (!ok) {
 		snd_printk("cmd: 0x%x failed at 0x%lx (status = 0x%x, data = 0x%x)\n", cmd, mpu->port, mpu->read(mpu, MPU401C(mpu)), mpu->read(mpu, MPU401D(mpu)));
-	// snd_printk("cmd: 0x%x at 0x%lx (status = 0x%x, data = 0x%x)\n", cmd, mpu->port, mpu->read(mpu, MPU401C(mpu)), mpu->read(mpu, MPU401D(mpu)));
+		return 1;
+	}
+	return 0;
 }
 
 /*
@@ -234,12 +236,19 @@ static int snd_mpu401_uart_input_open(sn
 	if (mpu->open_input && (err = mpu->open_input(mpu)) < 0)
 		return err;
 	if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode)) {
-		snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1);
-		snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1);
+		if (snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))
+			goto error_out;
+		if (snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1))
+			goto error_out;
 	}
 	mpu->substream_input = substream;
 	set_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
 	return 0;
+
+error_out:
+	if (mpu->open_input && mpu->close_input)
+		mpu->close_input(mpu);
+	return -EIO;
 }
 
 static int snd_mpu401_uart_output_open(snd_rawmidi_substream_t * substream)
@@ -251,39 +260,52 @@ static int snd_mpu401_uart_output_open(s
 	if (mpu->open_output && (err = mpu->open_output(mpu)) < 0)
 		return err;
 	if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode)) {
-		snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1);
-		snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1);
+		if (snd_mpu401_uart_cmd(mpu, MPU401_RESET, 1))
+			goto error_out;
+		if (snd_mpu401_uart_cmd(mpu, MPU401_ENTER_UART, 1))
+			goto error_out;
 	}
 	mpu->substream_output = substream;
 	set_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
 	return 0;
+
+error_out:
+	if (mpu->open_output && mpu->close_output)
+		mpu->close_output(mpu);
+	return -EIO;
 }
 
 static int snd_mpu401_uart_input_close(snd_rawmidi_substream_t * substream)
 {
 	mpu401_t *mpu;
+	int err = 0;
 
 	mpu = substream->rmidi->private_data;
 	clear_bit(MPU401_MODE_BIT_INPUT, &mpu->mode);
 	mpu->substream_input = NULL;
 	if (! test_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode))
-		snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
+		err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
 	if (mpu->close_input)
 		mpu->close_input(mpu);
+	if (err)
+		return -EIO;
 	return 0;
 }
 
 static int snd_mpu401_uart_output_close(snd_rawmidi_substream_t * substream)
 {
 	mpu401_t *mpu;
+	int err = 0;
 
 	mpu = substream->rmidi->private_data;
 	clear_bit(MPU401_MODE_BIT_OUTPUT, &mpu->mode);
 	mpu->substream_output = NULL;
 	if (! test_bit(MPU401_MODE_BIT_INPUT, &mpu->mode))
-		snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
+		err = snd_mpu401_uart_cmd(mpu, MPU401_RESET, 0);
 	if (mpu->close_output)
 		mpu->close_output(mpu);
+	if (err)
+		return -EIO;
 	return 0;
 }
 
-- 
1.1.3


-- 
Daniel T. Chen            crimsun at ubuntu.com
GPG key:   www.sh.nu/~crimsun/pubkey.gpg.asc
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