regmap: no indexed caching?

regmap: no indexed caching?

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 680 bytes --]

Hi,

indexed caching was removed from regmap (commit 4c691664583ef6a91f9ed0e08a75fbd30a5ffd5c)
saying:

    There should be no situation where it offers any advantage over rbtree
    and there are no current users so remove the code for simplicity.

What about devices having just a few registers (4 in my case)? I'd think
there are a number of such devices not yet converted to regmap. Is it
assumed that the additional overhead from rbtree-caching will make up
for the code saved?

Regards,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

Re: regmap: no indexed caching?

[Mark Brown]

On Thu, Jan 19, 2012 at 12:37:08PM +0100, Wolfram Sang wrote:

> What about devices having just a few registers (4 in my case)? I'd think
> there are a number of such devices not yet converted to regmap. Is it
> assumed that the additional overhead from rbtree-caching will make up
> for the code saved?

There should be vanishingly little overhead from the rbtree, you'll just
end up with a single cache node containing all the registers (unless
they're widely separated numerically) - it may even be faster as we
don't need to search the array looking for the index.