linux-kernel - Re: [PATCH V1] regmap: add bulk_write() for non-volatile register set

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Message-ID: <20120210110618.GB3056@opensource.wolfsonmicro.com>
Date:	Fri, 10 Feb 2012 11:06:19 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	gregkh@...uxfoundation.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH V1] regmap: add bulk_write() for non-volatile register set

On Fri, Feb 10, 2012 at 02:43:43PM +0530, Laxman Dewangan wrote:

Please remember to delete unnneded context from your mails, it makes it
much easier to find what you're saying.

> So I am going to allocate buffer for some size, initially
> min(val_bytes * max_register, 128) bytes, and in bulk_write(), if
> require buffer is more than 128 then re-alloc buffer which is now
> (req_size + 128).
> And then copy the data into this buffer, modify it and send to device.

What I'd suggest doing as a first pass is just allocating the buffer
each time, anything else is a performance optimisation we can worry
about incrementally.  Remember, this only has to be faster than I2C most
of the time and I2C is really slow.  For your case with 8 byte values
there's an even better optimisation which is to notice that we don't
need to swap at all and just use the original buffer directly.

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