lkml.org 
[lkml]   [2018]   [Sep]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 2/2] hwmon: ina3221: Add enable sysfs nodes
    Hello,

    On Wed, Sep 26, 2018 at 12:58:17PM -0700, Guenter Roeck wrote:
    > On Wed, Sep 26, 2018 at 11:02:44AM -0700, Nicolin Chen wrote:
    > > On Wed, Sep 26, 2018 at 06:06:32AM -0700, Guenter Roeck wrote:
    > > > On 09/25/2018 11:42 PM, Nicolin Chen wrote:
    > > > > The inX_enable interface allows user space to enable or disable
    > > > > the corresponding channel. Meanwhile, according to hwmon ABI, a
    > > > > disabled channel/sensor should return -ENODATA as a read result.
    > > > >
    > > > > However, there're configurable nodes sharing the same __show()
    > > > > functions. So this change also adds to check if the attribute is
    > > > > read-only to make sure it's not reading a configuration but the
    > > > > sensor data.
    > >
    > > > One necessary high level change I don't see below: With this change,
    > > > we should no longer drop a channel entirely if it is disabled from
    > > > devicetree. All channels should be visible but report -ENODATA if
    > > > disabled. In other words, it should be possible for the 'enable' flag
    > > > to override settings in DT.
    > >
    > > Hmm...I don't feel so convinced here. The status in DT binding isn't
    > > exactly a setting but a physical status: if a hardware design leaves
    > > a channel to be disconnected, I don't really see a point in enabling
    > > it in the runtime. Or maybe you can shed some light on it?
    > >
    >
    > You are making an assumption from your use case. It might as well be that
    > some or all channels are disabled in DT by default to conserve power,
    > not because they are disconnected.

    I think I probably should update my DT binding somehow to say it
    explicitly that the property should be only used in cases of the
    physical disconnections, although I feel the current binding "no
    input source" already has the same meaning.

    In my opinion, disabling channels in DT to save power isn't very
    plausible, because it sounds more likely a user decision, while,
    as we know, DT merely describes the hardware design.

    Otherwise, if we want something like a setting for this purpose,
    we should probably use a different property for DT binding, bool
    type "disable-on-boot" for example.

    > > Meanwhile, I believe the enable nodes are necessary in either way as
    > > users could decide to disable the connected channels, based on their
    > > use cases, to save power.
    > >
    > Agreed, though I would not say "necessary". "Useful" seems to be more
    > appropriate.

    Yea..

    \
     
     \ /
      Last update: 2018-09-26 22:26    [W:5.893 / U:1.656 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site