linux-kernel - Re: [RFC PATCH v2] regmap: smbus: add support for regmap over SMBus

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Message-ID: <20140414210429.GJ25182@sirena.org.uk>
Date:	Mon, 14 Apr 2014 22:04:29 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Shuge <shuge@...winnertech.com>, kevin@...winnertech.com,
	Chen-Yu Tsai <wens@...e.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Carlo Caione <carlo@...one.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dev@...ux-sunxi.org
Subject: Re: [RFC PATCH v2] regmap: smbus: add support for regmap over SMBus

On Mon, Apr 14, 2014 at 03:08:05PM +0200, Boris BREZILLON wrote:
> SMBus is a subset of the I2C protocol, oftenly used to access registers on
> external devices.

This is basically fine.  However...

> +	switch (ctx->transfer_type) {
> +	case REGMAP_SMBUS_BYTE_TRANSFER:
> +		while (count > 0 && !ret) {
> +			ret = i2c_smbus_write_byte_data(ctx->i2c, reg++,
> +							*(u8 *)data++);
> +
> +			count--;
> +		}
> +		break;

The transfer type gets set once per device at init time so why not just
parameterise based on val_bytes?

> +	case REGMAP_SMBUS_I2C_BLOCK_TRANSFER:
> +		while (count > 0 && !ret) {
> +			ret = i2c_smbus_write_i2c_block_data(ctx->i2c,
> +							     reg,
> +							     ctx->val_bytes,
> +							     (const u8 *)data);

Fix the const correctness of the API rather than casting.

> +			reg += ctx->val_bytes;
> +			count -= ctx->val_bytes;
> +			data += ctx->val_bytes;
> +		}

I'm assuming this will only be used if val_bytes isn't 1 or 2?

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