Automatic load of PCI kernel modules [WAS: [RFT] Automatic load of USB kernel modules]

Warner Losh imp at
Sun Jun 26 06:02:21 UTC 2011

On Jun 25, 2011, at 11:38 PM, Hans Petter Selasky wrote:

> On Saturday 25 June 2011 19:07:01 Hans Petter Selasky wrote:
>> On Saturday 25 June 2011 18:45:14 Warner Losh wrote:
>>> On Jun 25, 2011, at 9:42 AM, Hans Petter Selasky wrote:
>>>> On Saturday 25 June 2011 01:05:26 Jeremy Messenger wrote:
>>>>> Jeremy Messenger
>>>> Done.
>>> Please move it back.  It doesn't belong in /etc/defaults.  It belongs in
>>> /etc/devd if we're going to have it at all.  If you have a full GENERIC
>>> kernel, there will never be a NOMATCH line generated, so these entries
>>> will just be ignored.
>>> Warner
>> Done.
> Hi,
> I see that a lot of PCI device drivers use code to check their ID's.
> One simple way to dump all the PCI device ID's is to compile or load all 
> modules and then make a dummy PCI device, which only calls device_probe on the 
> full 32-bit space of the pci_get_devid(). This should take in matter of some 
> minutes to produce a complete list of PCI ID's. Then add these ID's to all the 
> respective drivers like a generic device ID table:
> struct pci_device_id {
> 	uint32_t device_id;
> 	uint32_t card_id;
> 	const char *description;
> 	unsigned long driver_info;
> } __aligned(32);
> Then export those automatically generated structures into the "pci_device_id" 
> section and have tools/bus_autoconf generate the matching rules.
> PCI format structure for bus_autoconf:
> "pci_device_id{256,:}"
> "device_id[0]{" U32_XOR ",8}"
> "device_id[1]{" U32_XOR ",8}"
> "device_id[2]{" U32_XOR ",8}"
> "device_id[3]{" U32_XOR ",8}"
> "card_id[0]{" U32_XOR ",8}"
> "card_id[1]{" U32_XOR ",8}"
> "card_id[2]{" U32_XOR ",8}"
> "card_id[3]{" U32_XOR ",8}"

I like the idea of having a standardized table.  I've done this with PC Card and it really works well.  It isn't the design pattern that all drivers use, and it may be hard to get everyone lined up on this.  I tried PCI back after I did PC Card and met resistance.  Most of the resistance was from people that are no longer active in the project, so I think that we could do this today.   I suspect that some of the vendor drivers today might stand in the way of having PCI be completely uniform.

The big advantage of USB is that it is uniform now.  PCI isn't.  It would take a lot of work to make it uniform.

Also, like I was saying on IRC, I don't like the fact that we have to have different bus code in this automatic tool.  It shouldn't know nor care about what the bus or drivers do.  The drivers should export a table and a descriptor for the table that would allow it to either generate the devd.conf lines needed to do the matching, or for some other program to examine the pnp_string information from newbus and figure out which module(s) to load.  Also, I don't find the above syntax easy to read or understand (sorry).

Don't get me wrong.  I love the USB autoload code you've done so far, but I consider it more of a prototype for the final system than the final system itself.


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