Re: [RFC v5 net-next 08/13] mfd: add interface to check whether a device is mfd
From: Colin Foster <colin.foster@in-advantage.com>
Date: 2021-12-30 02:04:52
Also in:
linux-gpio, lkml
On Wed, Dec 29, 2021 at 03:25:55PM +0000, Lee Jones wrote:
On Sat, 18 Dec 2021, Colin Foster wrote:quoted
Some drivers will need to create regmaps differently based on whether they are a child of an MFD or a standalone device. An example of this would be if a regmap were directly memory-mapped or an external bus. In the memory-mapped case a call to devm_regmap_init_mmio would return the correct regmap. In the case of an MFD, the regmap would need to be requested from the parent device. This addition allows the driver to correctly reason about these scenarios. Signed-off-by: Colin Foster <colin.foster@in-advantage.com> --- drivers/mfd/mfd-core.c | 5 +++++ include/linux/mfd/core.h | 10 ++++++++++ 2 files changed, 15 insertions(+)diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c index 684a011a6396..905f508a31b4 100644 --- a/drivers/mfd/mfd-core.c +++ b/drivers/mfd/mfd-core.c@@ -33,6 +33,11 @@ static struct device_type mfd_dev_type = { .name = "mfd_device", }; +int device_is_mfd(struct platform_device *pdev) +{ + return (!strcmp(pdev->dev.type->name, mfd_dev_type.name)); +} +Why is this device different to any other that has ever been mainlined?
Hi Lee, First, let me apologize for not responding to your response from the related RFC from earlier this month. It had been blocked by my spam filter and I had not seen it until just now. I'll have to check that more diligently now. Moving on... That's a question I keep asking myself. Either there's something I'm missing, or there's something new I'm doing. This is taking existing drivers that work via MMIO regmaps and making them interface-independent. As Vladimir pointed out here: https://lore.kernel.org/all/20211204022037.dkipkk42qet4u7go@skbuf/T/ (local) device_is_mfd could be dropped in lieu of an mfd-specific probe function. If there's something I'm missing, please let me know. But it feels like devm_get_regmap_from_resource at the end of the day would be the best solution to the design, and that doesn't exist. And implementing something like that is a task that I feel I'm not capable of tackling at this time.
-- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog