Messages in this thread | | | Date | Sun, 22 Aug 2004 23:02:47 +0000 | From | John Lenz <> | Subject | Re: platform bus, usage? |
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On 08/22/04 15:45:58, Pierre Ossman wrote: > I'm in the process of writing a driver for a SD/MMC card reader. > Since this is the first driver I'm writing I'm having some > difficulties fitting it into the linux driver model. I've read all > the documentation I can find to no avail. > > The device is attached to the LPC bus and cannot be found using PNP. > From what I can gather this driver should therefore be organised > under the platform bus. I can't figure out how to do this though. > I've created the device structure, with platform_bus_type at .bus. > I've called device_register with the structure. Now how to I create a > device object and attach this to the bus? With PCI I guess this > handles itself using the PCI id:s. > > At the moment I just let the driver play by itself. But that doesn't > seem to be using the driver model properly. > > Any pointers would be helpful. Documentation, functions, example > drivers, anything.
First example that comes to mind is the pxafb framebuffer device. The framebuffer device_driver is implemented in drivers/video/pxafb.c. The actual devices are implemented in various files in arch/arm/mach-pxa, for example, take a look at arch/arm/mach-pxa/generic.c
It is a little confusing, becuase the driver just uses a normal device_driver structure, but for the actual device, you need to create and register a platform_device structure.
So the driver has something like this static struct device_driver pxafb_driver = { .name = "pxa2xx-fb", .bus = &platform_bus_type, .probe = pxafb_probe, #ifdef CONFIG_PM .suspend = pxafb_suspend, .resume = pxafb_resume, #endif };
registered with a normal driver_register.
the actual device looks like static struct platform_device pxafb_device = { .name = "pxa2xx-fb", .id = -1, .dev = { .platform_data = &pxa_fb_info, .dma_mask = &fb_dma_mask, .coherent_dma_mask = 0xffffffff, }, .num_resources = ARRAY_SIZE(pxafb_resources), .resource = pxafb_resources, }; and it is registered with platform_add_devices.
Notice the two names are the same. Devices and drivers on the platform bus are matched by name. (see platform_match function in drivers/base/ platform.c)
Hope that helps, John
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