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Date: Tue, 23 Jun 2020 14:47:28 +0200 From: Michael Walle <michael@...le.cc> To: Sungbo Eo <mans0n@...ani.run> Cc: Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <bgolaszewski@...libre.com>, linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org Subject: Re: [PATCH] gpio: add GPO driver for PCA9570 Hi Sungbo, Am 2020-06-23 14:22, schrieb Sungbo Eo: > On 2020-06-23 17:31, Michael Walle wrote: >> Am 2020-06-23 08:05, schrieb Sungbo Eo: >>> This patch adds support for the PCA9570 I2C GPO expander. >>> >>> Signed-off-by: Sungbo Eo <mans0n@...ani.run> >>> --- >>> Tested in kernel 5.4 on an ipq40xx platform. >>> >>> This is my first time submitting a whole driver patch, and I'm not >>> really familiar with this PCA expander series. >>> Please let me know how I can improve this patch further. (Do I also >>> need to document the DT compatible string?) >> >> Did you have a look at drivers/gpio/gpio-regmap.c ? Your driver seems >> to be simple enough to be easily integrated with that. If you need a >> blueprint; because at the moment there is no driver in the kernel >> using that, you could have a look at: >> https://lore.kernel.org/linux-gpio/20200604211039.12689-7-michael@walle.cc/ > > Thanks for your advice. I didn't really know what regmap is for... > It seems gpio-regmap is for gpio controllers having val/dir registers. > But pca9570 does not use port registers. The master only sends a data > byte without reg address. Ahh I missed that :( > I'm not sure how to apply gpio-regmap or > regmap-i2c here. > I'll try to investigate if setting reg_size or reg_bits to zero is > possible. > > Please correct me if I'm in the wrong direction. That won't work because the underlying regmap expects the address bits to be either 8 or 16. In this case I'd guess gpio-regmap, doesn't make sense, because there is actually no real gain. -michael
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