Re: [PATCH 1/2] regmap: Add range check in _regmap_raw_read()

From: Srinivas Kandagatla
Date: Thu Feb 19 2015 - 06:04:48 EST

On 19/02/15 10:27, Mark Brown wrote:
On Thu, Feb 19, 2015 at 08:40:39AM +0000, Srinivas Kandagatla wrote:

+ /* Check for readable registers before we start */
+ for (i = 0; i < count; i++)
+ if (!regmap_readable(map, reg + (i * map->reg_stride)))
+ return -EINVAL;

That's starting to look pretty expensive especially if what we're
looking for is just max_register really... This is one of the reasons
Yes, I totally agree, this call would be expensive.

Initially I had some thing like this, and it works for me.

+ if (map->max_register &&
+ (reg > map->max_register ||
+ ((reg + (count - 1) * map->reg_stride) > map->max_register)))
+ return -EINVAL;

we're not religious about checking for readability everywhere, and
obviously even if we avoid triggering this particular thing we still
have to cope with both the caller and devices that didn't specify
readability. A cheaper check for just max_register would be less
concerning but it feels like we're trying to paper over a symptom with
this rather than fix a problem.
Yes, just checking max_register would solve the issue for me, I think I over done the patch.. I will resend with just max_register check.

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