linux-kernel - Re: [PATCH] i2c / ACPI: Do not touch an I2C device if it belongs to another adapter

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Message-ID: <20160920104523.GP1811@lahna.fi.intel.com>
Date:   Tue, 20 Sep 2016 13:45:23 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Nicolai Stange <nicstange@...il.com>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Octavian Purdila <octavian.purdila@...el.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c / ACPI: Do not touch an I2C device if it belongs to
 another adapter

On Tue, Sep 20, 2016 at 12:32:11PM +0200, Nicolai Stange wrote:
> Your patch fixes my issue, so feel free to add a
> 
>   Tested-by: Nicolai Stange <nicstange@...il.com>

Thanks!

> for this either.
> 
> But please see my remark below.
> 
> 
> Mika Westerberg <mika.westerberg@...ux.intel.com> writes:
> 
> > When enumerating I2C devices connected to an I2C adapter we scan the whole
> > namespace (as it is possible to have devices anywhere in that namespace,
> > not just below the I2C adapter device) and add each found device to the I2C
> > bus in question.
> >
> > Now after commit 525e6fabeae2 ("i2c / ACPI: add support for ACPI
> > reconfigure notifications") checking of the adapter handle to the one found
> > in the I2cSerialBus() resource was moved to happen after resources of the
> > I2C device has been parsed. This means that if the I2cSerialBus() resource
> > points to an adapter that does not exists in the system we still parse
> > those resources. This is problematic in particular because
> > acpi_dev_resource_interrupt() tries to configure GSI if the device also has
> > an Interrupt() resource. Failing to do that results errrors like this to be
> > printed on the console:
> >
> >   [   10.409490] ERROR: Unable to locate IOAPIC for GSI 37
> >
> > To fix this we pass the I2C adapter to i2c_acpi_get_info() and make sure
> > the handle matches the one in the I2cSerialBus() resource before doing
> > anything else to the device.
> >
> > Reported-by: Nicolai Stange <nicstange@...il.com>
> > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > ---
> >  drivers/i2c/i2c-core.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> > index c61c961cf8f9..eb32cb783fc8 100644
> > --- a/drivers/i2c/i2c-core.c
> > +++ b/drivers/i2c/i2c-core.c
> > @@ -168,6 +168,7 @@ static int i2c_acpi_do_lookup(struct acpi_device *adev,
> >  
> >  static int i2c_acpi_get_info(struct acpi_device *adev,
> >  			     struct i2c_board_info *info,
> > +			     struct i2c_adapter *adapter,
> >  			     acpi_handle *adapter_handle)
> >  {
> >  	struct list_head resource_list;
> > @@ -182,6 +183,10 @@ static int i2c_acpi_get_info(struct acpi_device *adev,
> >  	if (ret)
> >  		return ret;
> >  
> > +	/* The adapter must match the one in I2cSerialBus() connector */
> > +	if (adapter && ACPI_HANDLE(&adapter->dev) != lookup.adapter_handle)
> > +		return -ENODEV;
> > +
> 
> Would it be sensible to add the adapter presence check you provided
> earlier, i.e.
> 
> +	else if (!adapter) {
> +		/* The adapter must be present */
> +		if (acpi_bus_get_device(lookup.adapter_handle, &adapter_adev))
> +			return -ENODEV;
> +		if (acpi_bus_get_status(adapter_adev) || !adapter_adev->status.present)
> +			return -ENODEV;
> +
> +	}
> 
> 
> here, because we can't know if ...
> 
> 
> >  	info->fwnode = acpi_fwnode_handle(adev);
> >  	*adapter_handle = lookup.adapter_handle;
> >  
> > @@ -231,10 +236,7 @@ static acpi_status i2c_acpi_add_device(acpi_handle handle, u32 level,
> >  	if (acpi_bus_get_device(handle, &adev))
> >  		return AE_OK;
> >  
> > -	if (i2c_acpi_get_info(adev, &info, &adapter_handle))
> > -		return AE_OK;
> > -
> > -	if (adapter_handle != ACPI_HANDLE(&adapter->dev))
> > +	if (i2c_acpi_get_info(adev, &info, adapter, &adapter_handle))
> >  		return AE_OK;
> >  
> >  	i2c_acpi_register_device(adapter, adev, &info);
> > @@ -368,7 +370,7 @@ static int i2c_acpi_notify(struct notifier_block *nb, unsigned long value,
> >  
> >  	switch (value) {
> >  	case ACPI_RECONFIG_DEVICE_ADD:
> > -		if (i2c_acpi_get_info(adev, &info, &adapter_handle))
> > +		if (i2c_acpi_get_info(adev, &info, NULL, &adapter_handle))
> >  			break;
> 
> ... the ACPI device added here is physically existent?

Good point.

> 
> >  
> >  		adapter = i2c_acpi_find_adapter_by_handle(adapter_handle);
> 
> I suppose that it is always true that adev has been LoadTable()'d from
> some SSDT? Can't this SSDT be just as broken as my DSDT is? Not that
> I've seen such a case in the real world, I'm just asking.

Yes it can be broken and since the adapter reference is just a string in
I2cSerialBus() resource we definitely need to check that it actually
exists.

I'll submit v2 soon.