On 06/25/2016 05:53 PM, Dmitry Torokhov wrote: > On Sat, Jun 25, 2016 at 10:34:04AM +0200, Neil Armstrong wrote: >> On 06/25/2016 12:07 AM, Dmitry Torokhov wrote: >>> On Fri, Jun 24, 2016 at 11:18:04AM +0200, Neil Armstrong wrote: >>>> In order to support pwrkey for Qualcomm MDM9615 SoC, add support >>>> for the pm8018 pwrkey in pmic8xxx-pwrkey. >>>> >>>> Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> >>>> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx> >>> >>> NAK. >> >> Hi Dmitry, >> >> Actually, the new compatible string make sense, because the driver is compatible with the >> "pm8018" pwrkey but from a system point of view, it's not a pm8921 pwrkey, hence the new >> compatible string. > > A lot of systems note this fact in DTS, but not require driver changes, > by specifying several compatible strings: > > compatible = "nvidia,tegra114-sdhci", "nvidia,tegra30-sdhci"; > compatible = "fsl,imx6q-i2c", "fsl,imx21-i2c"; > compatible = "rockchip,rk3036-timer", "rockchip,rk3288-timer"; Sure, your point is valid. But here, the situation is quite different, the question is about confidence. >From the system point of view, I'm 100% sure there is a pm8010-pwrkey variant here, but I`m not convinced at all how it is similar from the 8921 version. >From the software point of view, I'm 80% sure the *actual* driver in it current form somehow works for the pm8018-pwrkey, not more. If somehow the driver is updated to support a 8921 feature that is not supported by the 8018 version, it will rely on the compatible string to make this a smart move. Since I do not have the pm8018 datasheet and the 8921 either, I cannot statue on this, So the smartest move from my side is to actually have a different compatible string to avoid future blocking situations. >> >> Rob Herring was very clear with me with this policy, and it will simplify further driver > > Could I get a pointer to this discussion so I can educate myself better > about DT policies? I had quite a lot of comments on the OXNAS support push (started here https://lkml.org/lkml/2016/3/3/495) were the policy was to narrow the new compatible strings to a SoC specific naming. For the qcom driver, the strings the already compliant and why not continue with the pm8018 ? >> architecture change since it will not imply devicetree changes anymore. > > Would we need the driver changes? What are the differences in power key > functionality between 8018 and 8921? You raise the biggest question, I do not know, so why should we say the pm8018-pwrkey /is/ compatible with pm8921-pwronly only by looking existing driver ? >> >> My point of view is that the devicetree describes the hardware and need to have SoC specific >> compatible string since it describes the actual silicon, and drivers must make sure to handle >> all the SoC or family variants using the compatible string and the match data. > > No, the compatible string means that the hardware is *compatible* with > something. It does not mean that we need to adjust driver every time a > company pumps out a new package including said hardware. It was something that I questionned myself about, but it seems the maintainers agrees quite easily to accept these compatible adding patches like the USB Ids or PCI ids patches. Regards, Neil > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
