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Message-ID: <20171104005327.GC24317@fury>
Date: Fri, 3 Nov 2017 17:53:27 -0700
From: Darren Hart <dvhart@...radead.org>
To: Mario Limonciello <mario.limonciello@...l.com>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>,
LKML <linux-kernel@...r.kernel.org>,
platform-driver-x86@...r.kernel.org, pali.rohar@...il.com
Subject: Re: [PATCH 2/2] platform/x86: dell-*wmi*: Relay failed initial probe
to dependent drivers
On Fri, Nov 03, 2017 at 11:27:22AM -0500, 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
Userspace shouldn't be able to remove the dell-wmi-descriptor driver if a
dependent driver is loaded. It isn't clear to me in which scenario we encounter
this problem ??
> should still be verified to return success values otherwise deferred
> probing be used.
The part after "otherwise" is breaking my English parser...
Should this read: "Userspace can unbind the driver, so all methods used from the
driver should still be verified to return successful values, falling back to
deferred probing in case of failure." ??
> 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:
This should trigger a checkpatch error, but doesn't. Huh. For everything but
"net", comment blocks should start with /* and not following text.
/*
* First line.
* Second line.
*/
A nit, and I can clean up if no changes are deemed necessary here.
> + * -EPROBE_DEFER: probing for dell-wmi-descriptor not yet run
> + * 0: valid descriptor, successfully probed
> + * < 0: invalid descriptor, don't probe dependent devices
> + */
--
Darren Hart
VMware Open Source Technology Center
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