linux-kernel - Re: [PATCH v6 2/4] i2c: npcm: Modify the client address assignment

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Message-ID: <CACD3sJY_79_VTe1EHPdh-1+FCBwb2KCW_N19==TMHAsrFL-rzg@mail.gmail.com>
Date: Fri, 11 Oct 2024 21:44:42 +0800
From: Tyrone Ting <warp5tw@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: avifishman70@...il.com, tmaimon77@...il.com, tali.perry1@...il.com, 
	venture@...gle.com, yuenn@...gle.com, benjaminfair@...gle.com, 
	andi.shyti@...nel.org, wsa@...nel.org, rand.sec96@...il.com, 
	wsa+renesas@...g-engineering.com, tali.perry@...oton.com, 
	Avi.Fishman@...oton.com, tomer.maimon@...oton.com, KWLIU@...oton.com, 
	JJLIU0@...oton.com, kfting@...oton.com, openbmc@...ts.ozlabs.org, 
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/4] i2c: npcm: Modify the client address assignment

Hi Andy:

Thank you for your comments.

Andy Shevchenko <andriy.shevchenko@...ux.intel.com> 於 2024年10月11日 週五 下午7:00寫道：
>
> On Fri, Oct 11, 2024 at 01:52:29PM +0800, Tyrone Ting wrote:
> > From: Tyrone Ting <kfting@...oton.com>
> >
> > Store the client address earlier since it might get called in
> > the i2c_recover_bus() logic flow at the early stage of
> > npcm_i2c_master_xfer().
>
> ...
>
> > +     /*
> > +      * Previously, the address was stored w/o left-shift by one bit and
> > +      * with that shift in the following call to npcm_i2c_master_start_xmit().
> > +      *
> > +      * Since there are cases that the i2c_recover_bus() gets called at the
> > +      * early stage of npcm_i2c_master_xfer(), the address is stored with
> > +      * the shift and used in the i2c_recover_bus().
> > +      *
> > +      * The address is stored from bit 1 to bit 7 in the register for
> > +      * sending the i2c address later so it's left-shifted by 1 bit.
> > +      */
>
> I would rephrase it a bit like
>
>         /*
>          * Previously, the 7-bit address was stored and being converted to
>          * the address of event in the following call to npcm_i2c_master_start_xmit().
>          *
>          * Since there are cases that the i2c_recover_bus() gets called at the
>          * early stage of npcm_i2c_master_xfer(), the address of event is stored
>          * and then used in the i2c_recover_bus().
>          */
>
> (E.g., the last paragraph just describes 101 about I2C 7-bit addresses usage
>  and may be dropped completely.)
>

Understood. I'll modify the comments and remove the last paragraph.

> > +     bus->dest_addr = i2c_8bit_addr_from_msg(msg0);
>
> ...
>
> > +             /*
> > +              * Since the transfer might be a read operation, remove the I2C_M_RD flag
> > +              * from the bus->dest_addr for the i2c_recover_bus() call later.
> > +              *
> > +              * The i2c_recover_bus() uses the address in a write direction to recover
> > +              * the i2c bus if some error condition occurs.
> > +              */
>
> > +             if (bus->dest_addr & I2C_M_RD)
>
> Redundant.
>

Just to double check. Is the code "if (bus->dest_addr & I2C_M_RD)" redundant?

> > +                     bus->dest_addr &= ~I2C_M_RD;
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Thank you again.

Regards,
Tyrone