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Date:   Tue, 08 Feb 2022 15:36:08 +0100
Message-ID: <s5h4k59s9wn.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Alexander Sergeyev <sergeev917@gmail.com>
Cc:     Jeremy Szu <jeremy.szu@canonical.com>, tiwai@suse.com,
        "moderated list:SOUND" <alsa-devel@alsa-project.org>,
        Kailang Yang <kailang@realtek.com>,
        open list <linux-kernel@vger.kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        Jian-Hong Pan <jhp@endlessos.org>,
        Hui Wang <hui.wang@canonical.com>,
        PeiSen Hou <pshou@realtek.com>
Subject: Re: [PATCH 1/4] ALSA: hda/realtek: fix mute/micmute LEDs for HP 855 G8
In-Reply-To: <s5htudk9cn3.wl-tiwai@suse.de>
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On Mon, 31 Jan 2022 15:57:04 +0100,
Takashi Iwai wrote:
> 
> On Sun, 30 Jan 2022 12:10:20 +0100,
> Alexander Sergeyev wrote:
> > What is also interesting, unbind & bind consistently fails on 31th bind:
> > 
> > echo -n '0000:05:00.6' > /sys/bus/pci/drivers/snd_hda_intel/bind
> > -bash: echo: write error: No such device
> > 
> > And does not recover from there until a reboot.
> 
> This is intended behavior.  The driver has a static device index that
> is incremented at each probe, so that the driver may probe multiple
> instances.  It'll be tricky to reset this for dynamic binding,
> though.  This problem is not only for HD-audio but for most of other
> drivers.  But I leave this as is for now, since the dynamic binding is
> rarely used for PCI and other buses, so far.

... and here is a fix patch for allowing more rebinds.
Give it a try.


Takashi

-- 8< --
From: Takashi Iwai <tiwai@suse.de>
Subject: [PATCH] ALSA: hda: Fix driver index handling at re-binding

HD-audio driver handles the multiple instances and keeps the static
index that is incremented at each probe.  This becomes a problem when
user tries to re-bind the device via sysfs multiple times; as the
device index isn't cleared unlike rmmod case, it points to the next
element at re-binding, and eventually later you can't probe any more
when it reaches to SNDRV_CARDS_MAX (usually 32).

This patch is an attempt to improve the handling at rebinding.
Instead of a static device index, now we keep a bitmap and assigns to
the first zero bit position.  At the driver remove, in return, the
bitmap slot is cleared again, so that it'll be available for the next
probe.

Reported-by: Alexander Sergeyev <sergeev917@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/pci/hda/hda_intel.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index 4b0338c4c543..a2922233e85f 100644
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -2064,14 +2064,16 @@ static const struct hda_controller_ops pci_hda_ops = {
 	.position_check = azx_position_check,
 };
 
+static DECLARE_BITMAP(probed_devs, SNDRV_CARDS);
+
 static int azx_probe(struct pci_dev *pci,
 		     const struct pci_device_id *pci_id)
 {
-	static int dev;
 	struct snd_card *card;
 	struct hda_intel *hda;
 	struct azx *chip;
 	bool schedule_probe;
+	int dev;
 	int err;
 
 	if (pci_match_id(driver_denylist, pci)) {
@@ -2079,10 +2081,11 @@ static int azx_probe(struct pci_dev *pci,
 		return -ENODEV;
 	}
 
+	dev = find_first_zero_bit(probed_devs, SNDRV_CARDS);
 	if (dev >= SNDRV_CARDS)
 		return -ENODEV;
 	if (!enable[dev]) {
-		dev++;
+		set_bit(dev, probed_devs);
 		return -ENOENT;
 	}
 
@@ -2149,7 +2152,7 @@ static int azx_probe(struct pci_dev *pci,
 	if (schedule_probe)
 		schedule_delayed_work(&hda->probe_work, 0);
 
-	dev++;
+	set_bit(dev, probed_devs);
 	if (chip->disabled)
 		complete_all(&hda->probe_wait);
 	return 0;
@@ -2372,6 +2375,7 @@ static void azx_remove(struct pci_dev *pci)
 		cancel_delayed_work_sync(&hda->probe_work);
 		device_lock(&pci->dev);
 
+		clear_bit(chip->dev_index, probed_devs);
 		pci_set_drvdata(pci, NULL);
 		snd_card_free(card);
 	}
-- 
2.34.1