linux-kernel - Re: [PATCH] regmap: irq: clear status when disable irq

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Message-ID: <20131015114812.GY2443@sirena.org.uk>
Date:	Tue, 15 Oct 2013 12:48:12 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Yi Zhang <yizhang@...vell.com>
Cc:	zhouqiao@...vell.com, zhangwm@...vell.com, yizhang.mrvl@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regmap: irq: clear status when disable irq

On Tue, Oct 15, 2013 at 01:03:58PM +0800, Yi Zhang wrote:

> +			bits_length = d->map->format.val_bytes * BITS_PER_BYTE;
> +			for (j = 0; j < bits_length; j++) {
> +				d->mask_buf[i] &= (0x1 << j);
> +				if (!d->mask_buf[i])
> +					ret = regmap_update_bits(d->map, reg,
> +								 (0x1 << j), 0);
> +				if (ret != 0)
> +					dev_err(d->map->dev, "Failed to ack 0x%x: %d\n",
> +						reg, ret);

I don't entirely understand this code - what's the loop doing?  It
looks like it's trying to acknowledge things bit by bit but it's doing
this by updating mask_buf so it looks like it'll corrupt the set of
masked interrupts.  After the zeroth iteration any bits other than bit 0
should get cleared by the &= (0x1 << j).  I'd have expected to just
write mask_buf back or something similar.

It's possible I'm missing something here but if that is the case perhaps
some comments would be good.

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