linux-kernel - RE: [PATCH v2 0/2] Add a property in at24.c

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Message-ID: <6F87890CF0F5204F892DEA1EF0D77A59813CA31B@fmsmsx124.amr.corp.intel.com>
Date:   Tue, 26 Jun 2018 16:31:58 +0000
From:   "Mani, Rajmohan" <rajmohan.mani@...el.com>
To:     "Yeh, Andy" <andy.yeh@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bartosz Golaszewski <brgl@...ev.pl>
CC:     "Chiang, AlanX" <alanx.chiang@...el.com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 0/2] Add a property in at24.c

Hi Bartosz,

> -----Original Message-----
> From: Yeh, Andy
> Sent: Tuesday, June 26, 2018 9:21 AM
> To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>; Bartosz
> Golaszewski <brgl@...ev.pl>
> Cc: Chiang, AlanX <alanx.chiang@...el.com>; linux-i2c <linux-
> i2c@...r.kernel.org>; Sakari Ailus <sakari.ailus@...ux.intel.com>; Mani,
> Rajmohan <rajmohan.mani@...el.com>; Andy Shevchenko
> <andy.shevchenko@...il.com>; Rob Herring <robh+dt@...nel.org>; Mark
> Rutland <mark.rutland@....com>; Arnd Bergmann <arnd@...db.de>; Greg
> Kroah-Hartman <gregkh@...uxfoundation.org>; Linux Kernel Mailing List
> <linux-kernel@...r.kernel.org>
> Subject: RE: [PATCH v2 0/2] Add a property in at24.c
> 
> > -----Original Message-----
> > From: Andy Shevchenko [mailto:andriy.shevchenko@...ux.intel.com]
> > Sent: Tuesday, June 26, 2018 11:48 PM
> > To: Bartosz Golaszewski <brgl@...ev.pl>
> > Cc: Chiang, AlanX <alanx.chiang@...el.com>; linux-i2c <linux-
> > i2c@...r.kernel.org>; Yeh, Andy <andy.yeh@...el.com>; Sakari Ailus
> > <sakari.ailus@...ux.intel.com>; Mani, Rajmohan
> > <rajmohan.mani@...el.com>; Andy Shevchenko
> > <andy.shevchenko@...il.com>; Rob Herring <robh+dt@...nel.org>; Mark
> > Rutland <mark.rutland@....com>; Arnd Bergmann <arnd@...db.de>; Greg
> > Kroah-Hartman <gregkh@...uxfoundation.org>; Linux Kernel Mailing List
> > <linux- kernel@...r.kernel.org>
> > Subject: Re: [PATCH v2 0/2] Add a property in at24.c
> >
> > On Tue, 2018-06-26 at 15:30 +0200, Bartosz Golaszewski wrote:
> > > 2018-06-26 15:23 GMT+02:00 Andy Shevchenko
> > <andriy.shevchenko@...ux.in
> > > tel.com>:
> > > > On Tue, 2018-06-26 at 14:36 +0200, Bartosz Golaszewski wrote:
> > > > > 2018-06-26 14:14 GMT+02:00 Andy Shevchenko
> > > > > <andriy.shevchenko@...ux.intel.com>:
> > > > > > On Tue, 2018-06-26 at 09:41 +0200, Bartosz Golaszewski wrote:
> > > > > > > What is your use case exactly? Do you have an EEPROM model
> > > > > > > that's not yet supported explicitly in the driver? Why would
> > > > > > > you need this option?
> > > > > >
> > > > > > The current at24 driver has no address width support,  thus,
> > > > > > reusing same
> > > > > > (allocated) IDs (non-DT case) is hard.
> > > >
> > > > ^^^^^
> > > >
> > > > > Every supported compatible has the width already specified in
> > > > > its corresponding chip data.
> > > >
> > > >
> > > > Please, read again carefully what I wrote before.
> > > >
> > >
> > > Ok makes sense in that case. Could you just point me towards an
> > > example model which has the address width different than the default
> > > for its type?
> >
> > AFAIK, it's a companion device inside the camera voice coil IC, i.e.
> > DONGWOON DW9714.
> >
> 
> Nope, actually it is DW9807 instead, which is used on a Samsung Chromebook.

M24C64S is one example, where reusing same id (non-DT case) is not possible,
since this model uses 16 bits as address width, as the driver supports only
8 bits address width as default.

Thanks
Raj