linux-kernel - Re: [PATCH 07/50] staging: omap-thermal: introduce RMW

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Message-ID: <20130316140042.GK9189@mwanda>
Date:	Sat, 16 Mar 2013 17:00:42 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Eduardo Valentin <eduardo.valentin@...com>
Cc:	gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH 07/50] staging: omap-thermal: introduce RMW_BITS macro

On Sat, Mar 16, 2013 at 08:36:51AM -0400, Eduardo Valentin wrote:
> >But that said, I don't care for the RMW_BITS() very much as a long
> >term thing.  If we just used pointers instead of passing the offset
> >into the bg_ptr->conf->sensors[] array then everything would be a
> >lot cleaner.
> >
> >In other words, instead of this:
> >
> >static u32 omap_bandgap_read_temp(struct omap_bandgap *bg_ptr, int id)
> >
> >We would have:
> >
> >static u32 omap_bandgap_read_temp(struct omap_bandgap *bg_ptr,
> >				  struct temp_sensor_registers *tsr)
> 
> I see. That will require a change in the whole driver though. If you
> see, the driver as of today uses the former approach, not only for
> read_temp or rmw_bits.

Yep.

> 
> >
> >If you have the pointer then it's easy write RMW_BITS() as a
> >function.
> >
> >static void rmw_bits(struct omap_bandgap *bg_ptr, u32 reg, u32 mask, u32 val)
> >{
> >	u32 r;
> >
> >	r = omap_bandgap_readl(bg_ptr, reg);
> >	r &= ~mask;
> >	r |= val << __ffs(mask);
> >	omap_bandgap_writel(bg_ptr, r, reg);
> >}
> >
> >It's called like:
> >
> >	rmw_bits(bg_ptr, tsr->bgap_mask_ctrl, tsr->mask_freeze_mask, 1);
> 
> This is nice, but it will require fetching tsr from .conf before
> every call o rmw_bits. And for that you need the sensor index.
> 

No.  I'm suggesting that you re-write the driver to pass the tsr
pointer directly instead of the index.

regards,
dan carpenter

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