lkml.org 
[lkml]   [2017]   [Nov]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/2] platform/x86: dell-*wmi*: Relay failed initial probe to dependent drivers
On Thursday 09 November 2017 16:13:52 Mario.Limonciello@dell.com wrote:
> > -----Original Message-----
> > From: Pali Rohár [mailto:pali.rohar@gmail.com]
> > Sent: Thursday, November 9, 2017 10:03 AM
> > To: Limonciello, Mario <Mario_Limonciello@Dell.com>
> > Cc: dvhart@infradead.org; Andy Shevchenko <andy.shevchenko@gmail.com>;
> > LKML <linux-kernel@vger.kernel.org>; platform-driver-x86@vger.kernel.org
> > Subject: Re: [PATCH 2/2] platform/x86: dell-*wmi*: Relay failed initial probe to
> > dependent drivers
> >
> > On Friday 03 November 2017 11:27:22 Mario Limonciello wrote:
> > > dell-wmi and dell-smbios-wmi are dependent upon dell-wmi-descriptor
> > > finishing probe successfully to probe themselves.
> > >
> > > Currently if dell-wmi-descriptor fails probing in a non-recoverable way
> > > (such as invalid header) dell-wmi and dell-smbios-wmi will continue to
> > > try to redo probing due to deferred probing.
> > >
> > > To solve this have the dependent drivers query the dell-wmi-descriptor
> > > driver whether the descriptor has been determined valid. The possible
> > > results are:
> > > -EPROBE_DEFER: Descriptor not yet probed, dependent driver should wait
> > > and use deferred probing
> > > < 0: Descriptor probed, invalid. Dependent driver should return an
> > > error.
> > > 0: Successful descriptor probe, dependent driver can continue
> > >
> > > Successful descriptor probe still doesn't mean that the descriptor driver
> > > is necessarily bound at the time of initialization of dependent driver.
> > > Userspace can unbind the driver, so all methods used from driver
> > > should still be verified to return success values otherwise deferred
> > > probing be used.
> >
> > Darren, Andy, any comments on this patch?
> >
> > I think now it should work also those corner, but legit cases.
> >
> > > Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> > > ---
> > > drivers/platform/x86/dell-smbios-wmi.c | 4 ++++
> > > drivers/platform/x86/dell-wmi-descriptor.c | 11 +++++++++++
> > > drivers/platform/x86/dell-wmi-descriptor.h | 7 +++++++
> > > drivers/platform/x86/dell-wmi.c | 5 +++++
> > > 4 files changed, 27 insertions(+)
> > >
> > > diff --git a/drivers/platform/x86/dell-smbios-wmi.c b/drivers/platform/x86/dell-
> > smbios-wmi.c
> > > index 35c13815b24c..3fa53fa174b2 100644
> > > --- a/drivers/platform/x86/dell-smbios-wmi.c
> > > +++ b/drivers/platform/x86/dell-smbios-wmi.c
> > > @@ -151,6 +151,10 @@ static int dell_smbios_wmi_probe(struct wmi_device
> > *wdev)
> > > if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
> > > return -ENODEV;
> > >
> > > + ret = dell_wmi_get_descriptor_valid();
> > > + if (ret)
> > > + return ret;
> > > +
> > > priv = devm_kzalloc(&wdev->dev, sizeof(struct wmi_smbios_priv),
> > > GFP_KERNEL);
> > > if (!priv)
> > > diff --git a/drivers/platform/x86/dell-wmi-descriptor.c
> > b/drivers/platform/x86/dell-wmi-descriptor.c
> > > index 28ef5f37cfbf..e7f4c3a7bfc4 100644
> > > --- a/drivers/platform/x86/dell-wmi-descriptor.c
> > > +++ b/drivers/platform/x86/dell-wmi-descriptor.c
> > > @@ -26,9 +26,16 @@ struct descriptor_priv {
> > > u32 interface_version;
> > > u32 size;
> > > };
> > > +static int descriptor_valid = -EPROBE_DEFER;
> > > static LIST_HEAD(wmi_list);
> > > static DEFINE_MUTEX(list_mutex);
> > >
> > > +int dell_wmi_get_descriptor_valid(void)
> > > +{
> > > + return descriptor_valid;
> > > +}
> > > +EXPORT_SYMBOL_GPL(dell_wmi_get_descriptor_valid);
> > > +
> > > bool dell_wmi_get_interface_version(u32 *version)
> > > {
> > > struct descriptor_priv *priv;
> > > @@ -91,6 +98,7 @@ static int dell_wmi_descriptor_probe(struct wmi_device
> > *wdev)
> > > if (obj->type != ACPI_TYPE_BUFFER) {
> > > dev_err(&wdev->dev, "Dell descriptor has wrong type\n");
> > > ret = -EINVAL;
> > > + descriptor_valid = ret;
> > > goto out;
> > > }
> > >
> > > @@ -102,6 +110,7 @@ static int dell_wmi_descriptor_probe(struct wmi_device
> > *wdev)
> > > "Dell descriptor buffer has unexpected length (%d)\n",
> > > obj->buffer.length);
> > > ret = -EINVAL;
> > > + descriptor_valid = ret;
> > > goto out;
> > > }
> > >
> > > @@ -111,8 +120,10 @@ static int dell_wmi_descriptor_probe(struct wmi_device
> > *wdev)
> > > dev_err(&wdev->dev, "Dell descriptor buffer has invalid signature
> > (%8ph)\n",
> > > buffer);
> > > ret = -EINVAL;
> > > + descriptor_valid = ret;
> > > goto out;
> > > }
> > > + descriptor_valid = 0;
> > >
> > > if (buffer[2] != 0 && buffer[2] != 1)
> > > dev_warn(&wdev->dev, "Dell descriptor buffer has unknown
> > version (%lu)\n",
> > > diff --git a/drivers/platform/x86/dell-wmi-descriptor.h
> > b/drivers/platform/x86/dell-wmi-descriptor.h
> > > index 5f7b69c2c83a..776cddd5e135 100644
> > > --- a/drivers/platform/x86/dell-wmi-descriptor.h
> > > +++ b/drivers/platform/x86/dell-wmi-descriptor.h
> > > @@ -15,6 +15,13 @@
> > >
> > > #define DELL_WMI_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-
> > B622A1EF5492"
> > >
> > > +/* possible return values:
> > > + * -EPROBE_DEFER: probing for dell-wmi-descriptor not yet run
> > > + * 0: valid descriptor, successfully probed
> > > + * < 0: invalid descriptor, don't probe dependent devices
> > > + */
> > > +int dell_wmi_get_descriptor_valid(void);
> > > +
> > > bool dell_wmi_get_interface_version(u32 *version);
> > > bool dell_wmi_get_size(u32 *size);
> > >
> > > diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
> > > index 54321080a30d..bb7c1e681792 100644
> > > --- a/drivers/platform/x86/dell-wmi.c
> > > +++ b/drivers/platform/x86/dell-wmi.c
> > > @@ -655,10 +655,15 @@ static int dell_wmi_events_set_enabled(bool enable)
> > > static int dell_wmi_probe(struct wmi_device *wdev)
> > > {
> > > struct dell_wmi_priv *priv;
> > > + int ret;
> > >
> > > if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
> > > return -ENODEV;
> >
> > Just one suggestion, is above check still needed in dell-wmi.c code?
> > I think that now it should be job of dell_wmi_get_descriptor_valid()
> > function to fully validate if dell wmi descriptor driver is able to
> > provide all needed information for dell-wmi driver.
> >
>
> Yes, I believe it's still needed because if the GUID isn't on the bus the probe
> routine for dell-wmi-descriptor won't run and dell_wmi_get_descriptor_valid()
> will continually return -EPROBE_DEFER.
>
> That's the exact problem this patch exists for (preventing infinite deferred
> probing).
>
> Perhaps a "cleaner" solution is to have the init routine of dell-wmi-descriptor
> do this wmi_has_guid check and set the descriptor_valid variable to -ENODEV
> so that "dependent" drivers don't need to.

I understand. But I mean, if function dell_wmi_get_descriptor_valid()
should not do that check for DELL_WMI_DESCRIPTOR_GUID itself.

Because every driver which would use dell-wmi-descriptor needs to
do that check.

> > > + ret = dell_wmi_get_descriptor_valid();
> > > + if (ret)
> > > + return ret;
> > > +
> > > priv = devm_kzalloc(
> > > &wdev->dev, sizeof(struct dell_wmi_priv), GFP_KERNEL);
> > > if (!priv)
> >
> > --
> > Pali Rohár
> > pali.rohar@gmail.com

--
Pali Rohár
pali.rohar@gmail.com

\
 
 \ /
  Last update: 2017-11-09 18:29    [W:0.110 / U:0.264 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site