lkml.org 
[lkml]   [2020]   [Jun]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller
    Am 2020-06-10 09:19, schrieb Lee Jones:
    > On Wed, 10 Jun 2020, Michael Walle wrote:
    >> Am 2020-06-09 21:45, schrieb Lee Jones:
    >> > On Tue, 09 Jun 2020, Michael Walle wrote:
    >> > > > We do not need a 'simple-regmap' solution for your use-case.
    >> > > >
    >> > > > Since your device's registers are segregated, just split up the
    >> > > > register map and allocate each sub-device with it's own slice.
    >> > >
    >> > > I don't get it, could you make a device tree example for my
    >> > > use-case? (see also above)
    >> >
    >> > &i2cbus {
    >> > mfd-device@10 {
    >> > compatible = "simple-mfd";
    >> > reg = <10>;
    >> >
    >> > sub-device@10 {
    >> > compatible = "vendor,sub-device";
    >> > reg = <10>;
    >> > };
    >> > };
    >> >
    >> > The Regmap config would be present in each of the child devices.
    >> >
    >> > Each child device would call devm_regmap_init_i2c() in .probe().
    >>
    >> Ah, I see. If I'm not wrong, this still means to create an i2c
    >> device driver with the name "simple-mfd".
    >
    > Yes, it does.
    >
    >> Besides that, I don't like this, because:
    >> - Rob already expressed its concerns with "simple-mfd" and so on.
    >
    > Where did this take place? I'd like to read up on this.

    In this thread:
    https://lore.kernel.org/linux-devicetree/20200604211039.12689-1-michael@walle.cc/T/#m16fdba5962069e7cd4aa817582ee358c9fe2ecbf

    >
    >> - you need to duplicate the config in each sub device
    >
    > You can have a share a single config.
    >
    >> - which also means you are restricting the sub devices to be
    >> i2c only (unless you implement and duplicate other regmap configs,
    >> too). For this driver, SPI and MMIO may be viable options.
    >
    > You could also have a shared implementation to choose between different
    > busses.

    Then what is the difference between to have this shared config in the
    parent driver only and use the functions which are already there, i.e.
    dev_get_regmap(parent). But see, below, I'll wait with what you're
    coming up.

    >
    >> Thus, I'd rather implement a simple-mfd.c which implement a common
    >> I2C driver for now and populate its children using
    >> devm_of_platform_populate(). This could be extended to support other
    >> type of regmaps like SPI in the future.
    >>
    >> Also some MFD drivers could be moved to this, a likely candidate is
    >> the smsc-ece1099.c. Although I don't really understand its purpose,
    >> if don't have CONFIG_OF.
    >>
    >> Judging from the existing code, this simple-mfd.c wouldn't just be
    >> "a list of compatible" strings but also additional quirks and tweaks
    >> for particular devices in this list.
    >
    > Hold off on the simple-mfd.c idea, as I'm not taken by it yet and
    > wouldn't want you to waste your time. I have another idea which would
    > help. Give me a few days to put something together.

    Sure. I'm just glad there is now a discussion about this issue.

    -michael

    \
     
     \ /
      Last update: 2020-06-10 09:49    [W:6.039 / U:0.232 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site