Re: [PATCH] ALSA: hda: Use correct start/count for sysfs init

From: Takashi Iwai
Date: Wed Jun 26 2019 - 04:27:16 EST

On Tue, 25 Jun 2019 23:54:18 +0200,
Evan Green wrote:
> The normal flow through the widget sysfs codepath is that
> snd_hdac_refresh_widgets() is called once without the sysfs bool set
> to set up codec->num_nodes and friends, then another time with the
> bool set to actually allocate all the sysfs widgets. However, during
> the first time allocation, hda_widget_sysfs_reinit() ignores the new
> num_nodes passed in via parameter and just calls hda_widget_sysfs_init(),
> using whatever was in codec->num_nodes before the update. This is not
> correct in cases where num_nodes changes. Here's an example:
> Sometime earlier:
> snd_hdac_refresh_widgets(hdac, false)
> sets codec->num_nodes to 2, widgets is still not allocated
> Now:
> snd_hdac_refresh_widgets(hdac, true)
> hda_widget_sysfs_reinit(num_nodes=7)
> hda_widget_sysfs_init()
> widget_tree_create()
> alloc(codec->num_nodes) // this is still 2
> codec->num_nodes = 7
> Pass num_nodes and start_nid down into widget_tree_create() so that
> the right number of nodes are allocated in all cases.
> Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx>

Thanks for the patch. That's indeed a problem, but I guess a simpler
approach is just to return if sysfs didn't exist. If the sysfs
entries aren't present at the second call with sysfs=true, it implies
that the codec object will be exposed anyway later, and the sysfs will
be created there. So, something like below would work instead?



--- a/sound/hda/hdac_sysfs.c
+++ b/sound/hda/hdac_sysfs.c
@@ -428,7 +428,7 @@ int hda_widget_sysfs_reinit(struct hdac_device *codec,
int i;

if (!codec->widgets)
- return hda_widget_sysfs_init(codec);
+ return 0;

tree = kmemdup(codec->widgets, sizeof(*tree), GFP_KERNEL);
if (!tree)