No support of platform device instance id?

[Shawn Guo]

On Thu, Mar 17, 2011 at 11:08:19AM -0600, Grant Likely wrote:
> On Thu, Mar 17, 2011 at 12:31:15PM +0800, Shawn Guo wrote:
> > On Wed, Mar 16, 2011 at 05:05:00PM -0600, Grant Likely wrote:
> > > 
> > [...]
> > > I'd like to have feedback on the new code to make sure that the model
> > > is sane.  There are some fiddly code it there which is used to match
> > > platform_device registrations to nodes in the device tree.  I *think*
> > > it makes sense, but I'd like to hear other opinions.
> > > 
> > Binding platform_device with of_node via resources matching seems a
> > little fiddly, but your implementation looks solid to me.  I made a
> > quick scan on all the platform_device registration under
> > arch/arm/plat-mxc/devices, nothing would be broken, only except
> > platform-gpio_keys which is not an on-chip device.
> 
> Right; and doing it this way doesn't make sense for anything that is
> board/system specific because if the board is using the DT, then it is
> simpler and more reliable to avoid the matching heuristic entirely.
> 
> > Looking at the code, I'm wondering how the binding of resource type
> > IORESOURCE_DMA looks like.  I'm seeing some platform_device is using
> > this flag to tell dma channel fixed for the device.  I'm not sure if
> > it can be fit in property 'dma-ranges'.  And I only see IORESOURCE_MEM
> > and IORESOURCE_IRQ being used in the matching model.
> 
> The matching is simply a heuristic that makes a best guess about how
> how device nodes line up with platform_device registrations.  Right
> now the heuristic is to look at the register ranges and irqs described
> in the node and make sure that each of them are listed in the
> platform_device.  If the platform_device has additional resources,
> then it simply ignores them.  That seems to be sufficient for accurate
> matching, but I won't know for sure until people start using it.
> 
> If there are situations where the heuristic does not work, then I'd
> like to know what they are so that the algorithm can be fixed, or in
> the absolute worst case implement workaround logic.
> 
> One option I'm considering which would improve the accuracy of the
> heuristic is to add a 'char *of_compatible' field to struct
> platform_device.  Then platform_devices could optionally be tagged
> with the compatible value that must be present in order to be matched
> with a node.
> 
> I definitely want feedback on the matching heuristic!
> 
Tested on babbage with serial, fec and esdhc drivers, and I did see
it solves problems of clkdev dev_id matching and pdev->id use.  And
it even helped to discover one problem with .end definition of fec
resource IORESOURCE_MEM.  I will send mainline a patch for that soon.

-- 
Regards,
Shawn