Re: Grafting old platform drivers onto a new DT kernel

From: Mason
Date: Mon Nov 09 2015 - 12:04:08 EST

On 09/11/2015 17:12, Måns Rullgård wrote:

> Mason writes:
>> On 09/11/2015 16:40, Måns Rullgård wrote:
>>> The simplest solution for you is probably to add a quick and dirty DT
>>> binding to the old driver. If it doesn't use any driver-specific
>>> platform data struct, you only need to set .of_match_table in the
>>> struct platform_driver. If there is a platform data struct, you'll also
>>> need to write some code to populate it from DT properties. It shouldn't
>>> take more than a few minutes per driver in most cases.
>> I'll try that approach, although I fear that "a few minutes per driver"
>> is an optimistic assessment.
> If the driver only needs an MMIO region and an IRQ, it is literally five
> lines of code.

It took me 7 days to figure out there were 2 lines missing in the
interrupt controller driver.

My problem is that I don't understand the platform API, nor the
interaction with the DT API.

Let me see...

In arch/arm/mach-tangox/platform_dev.c

static struct platform_device tangox_sdhci0_device = { ... };
static struct platform_device tangox_sdhci1_device = { ... };

static void tangox_init_sdhci(void)
if (tangox_sdio_enabled(0))

if (tangox_sdio_enabled(1))

called from tangox_init_devices() which is marked arch_initcall.

In the driver

static struct platform_driver tangox_platform_sdio0 = {
.remove = sdhci_tangox_remove,
.suspend = sdhci_tangox_suspend,
.resume = sdhci_tangox_resume,
.driver = {
.name = "tangox-sdhci",
.owner = THIS_MODULE,

static struct platform_driver tangox_platform_sdio0 = {
.remove = sdhci_tangox_remove,
.driver = {
.name = "tangox-sdhci",
.owner = THIS_MODULE,

static int __init tangox_sdhci_drv_init(void) {
return platform_driver_probe(&tangox_platform_sdio0, sdhci_tangox_probe);

static void __exit tangox_sdhci_drv_exit(void) {


The old way:

1) call platform_device_register() with a "struct platform_device"
2) call platform_driver_probe with a "struct platform_driver"

The new way(?)

The mess in 2) is hidden behind module_platform_driver?
The platform_device_register() is done by the DT core?
The struct platform_driver requires a probe function?


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