linux-kernel - [PATCH 3.16 254/305] ALSA: usb-audio: Replace probing flag with active refcount

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Message-ID: <lsq.1549201508.762786632@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Takashi Iwai" <tiwai@...e.de>
Subject: [PATCH 3.16 254/305] ALSA: usb-audio: Replace probing flag with
 active refcount

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

commit a6da499b76b1a75412f047ac388e9ffd69a5c55b upstream.

We can use active refcount for preventing autopm during probe.

Signed-off-by: Takashi Iwai <tiwai@...e.de>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 sound/usb/card.c     | 12 ++++--------
 sound/usb/usbaudio.h |  1 -
 2 files changed, 4 insertions(+), 9 deletions(-)

--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -402,7 +402,7 @@ static int snd_usb_audio_create(struct u
 	chip->card = card;
 	chip->setup = device_setup[idx];
 	chip->autoclock = autoclock;
-	chip->probing = 1;
+	atomic_set(&chip->active, 1); /* avoid autopm during probing */
 	atomic_set(&chip->usage_count, 0);
 	atomic_set(&chip->shutdown, 0);
 
@@ -532,7 +532,7 @@ snd_usb_audio_probe(struct usb_device *d
 				goto __error;
 			}
 			chip = usb_chip[i];
-			chip->probing = 1;
+			atomic_inc(&chip->active); /* avoid autopm */
 			break;
 		}
 	}
@@ -588,7 +588,7 @@ snd_usb_audio_probe(struct usb_device *d
 
 	usb_chip[chip->index] = chip;
 	chip->num_interfaces++;
-	chip->probing = 0;
+	atomic_dec(&chip->active);
 	mutex_unlock(&register_mutex);
 	return chip;
 
@@ -596,7 +596,7 @@ snd_usb_audio_probe(struct usb_device *d
 	if (chip) {
 		if (!chip->num_interfaces)
 			snd_card_free(chip->card);
-		chip->probing = 0;
+		atomic_dec(&chip->active);
 	}
 	mutex_unlock(&register_mutex);
  __err_val:
@@ -712,8 +712,6 @@ int snd_usb_autoresume(struct snd_usb_au
 {
 	if (atomic_read(&chip->shutdown))
 		return -EIO;
-	if (chip->probing)
-		return 0;
 	if (atomic_inc_return(&chip->active) == 1)
 		return usb_autopm_get_interface(chip->pm_intf);
 	return 0;
@@ -721,8 +719,6 @@ int snd_usb_autoresume(struct snd_usb_au
 
 void snd_usb_autosuspend(struct snd_usb_audio *chip)
 {
-	if (chip->probing)
-		return;
 	if (atomic_dec_and_test(&chip->active))
 		usb_autopm_put_interface(chip->pm_intf);
 }
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -37,7 +37,6 @@ struct snd_usb_audio {
 	struct usb_interface *pm_intf;
 	u32 usb_id;
 	struct mutex mutex;
-	unsigned int probing:1;
 	unsigned int autosuspended:1;	
 	atomic_t active;
 	atomic_t shutdown;