Comment 11 for bug 399319

On 23.08.2009 01:14, Marc Tardif wrote:
> Instead of dumping raw text files which will change as new udev rules
> are introduced, I would propose that Launchpad exposes an API defining
> what it defines as a device. The current implementation is obviously
> coupled with what HAL defines as a device. Only a fraction of this
> information is actually used by Launchpad, so there seems to be a divide
> between both definitions.

Right, Launchpad uses only a relatively small part of that data.

But I am not sure if the client should do too much processing of the
data. If we notice an error, it is hard to fix, and we might need to
throw away lots of submissions. Errors during server processing are much
easier to track and to fix.

To give an example where things become a bit difficult: The kernel
controls most storage devices via the SCSI layer, meaning that we have
for nearly each IDE disk and nearly each USB stick a "virtual" SCSI
device, controlled by a "virtual" SCSI controller. If you have a look
into the LP file lib/canonical/launchpad/scripte/hwdb-submissions.py,
you'll see a number of other "special cases". The script may need
sometimes some additional data from parent devices. Hence I think it is
better to store all the data we get from udev (and at least some
additional data from the "attribute files" in sysfs.

>
> Without being intimately familiar with Launchpad internal requirements
> for devices, this is what I might propose as a schema to express each
> device:
>
> <define name="device">
> <interleave>
> <element name="bus">
> <attribute name="value">
> <text/>
> </attribute>
> </element>
> <optional>
> <element name="driver">
> <attribute name="value">
> <text/>
> </attribute>
> </element>
> </optional>
> <optional>
> <element name="vendor_id">
> <attribute name="value">
> <ref name="integer"/>
> </attribute>
> </element>
> <element name="product_id">
> <attribute name="value">
> <ref name="integer"/>
> </attribute>
> </element>
> </optional>

bus, vendor_id and product_id are all required attributes -- that's what
the LP database needs to identify a device.

> <optional>
> <element name="subvendor_id">
> <attribute name="value">
> <ref name="integer"/>
> </attribute>
> </element>
> <element name="subproduct_id">
> <attribute name="value">
> <ref name="integer"/>
> </attribute>
> </element>
> </optional>
> <optional>
> <element name="vendor">
> <attribute name="value">
> <text/>
> </attribute>
> </element>
> </optional>
> <optional>
> <element name="product">
> <attribute name="value">
> <text/>
> </attribute>
> </element>
> </optional>
> </interleave>
> </define>
>