linux-kernel - Re: [PATCH v5 2/2] i2c: i2c-ocores: Add support for the GRLIB port of the controller and use function pointers for getreg and setreg functions

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Message-ID: <87pq3e52z7.fsf@dell.be.48ers.dk>
Date:	Thu, 15 Nov 2012 15:56:44 +0100
From:	Peter Korsgaard <jacmet@...site.dk>
To:	Andreas Larsson <andreas@...sler.com>
Cc:	Wolfram Sang <w.sang@...gutronix.de>,
	Ben Dooks <ben-linux@...ff.org>, linux-i2c@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	software@...sler.com
Subject: Re: [PATCH v5 2/2] i2c: i2c-ocores: Add support for the GRLIB port of the controller and use function pointers for getreg and setreg functions

>>>>> "Andreas" == Andreas Larsson <andreas@...sler.com> writes:

 Andreas> The registers in the GRLIB port of the controller are 32-bit
 Andreas> and in big endian byte order. The PRELOW and PREHIGH registers
 Andreas> are merged into one register. The subsequent registers have
 Andreas> their offset decreased accordingly. Hence the register access
 Andreas> needs to be handled in a non-standard manner using custom
 Andreas> getreg and setreg functions.

 Andreas> The single oc_getreg and one oc_setreg functions, that
 Andreas> branches and call different ioread and iowrite functions, are
 Andreas> replaced by specific functions that uses the appropriate
 Andreas> ioread and iowrite functions and function pointers are
 Andreas> initiated and used to call the approproate functions.

 Andreas> A type is added as the data of the of match table entries. A
 Andreas> new entry with a different compatible string is added to the
 Andreas> table. The type of that entry triggers usage of the custom
 Andreas> grlib functions by setting the new getreg and setreg function
 Andreas> pointers to these functions.

Sorry to keep on requesting changes, but see below for a bit more:

 
 Andreas>  static void ocores_process(struct ocores_i2c *i2c)
 Andreas>  {
 Andreas>  	struct i2c_msg *msg = i2c->msg;
 Andreas> -	u8 stat = oc_getreg(i2c, OCI2C_STATUS);
 Andreas> +	u8 stat = i2c->getreg(i2c, OCI2C_STATUS);

The patch would have been quite a bit smaller/easier to read if you had
kept oc_getreg / oc_setreg as wrappers.

 
 Andreas>  #ifdef CONFIG_OF
 Andreas>  static int ocores_i2c_of_probe(struct platform_device *pdev,
 Andreas>  				struct ocores_i2c *i2c)
 Andreas>  {
 Andreas>  	struct device_node *np = pdev->dev.of_node;
 Andreas> +	const struct of_device_id *match;
 Andreas>  	u32 val;
 
 Andreas>  	if (of_property_read_u32(np, "reg-shift", &i2c->reg_shift)) {
 Andreas> @@ -257,6 +324,14 @@ static int ocores_i2c_of_probe(struct platform_device *pdev,
 
 Andreas>  	of_property_read_u32(pdev->dev.of_node, "reg-io-width",
 Andreas>  				&i2c->reg_io_width);
 Andreas> +
 Andreas> +	match = of_match_node(ocores_i2c_match, pdev->dev.of_node);
 Andreas> +	if (match && (int)match->data == TYPE_GRLIB) {
 Andreas> +		dev_dbg(&pdev->dev, "GRLIB variant of i2c-ocores\n");
 Andreas> +		i2c->setreg = oc_setreg_grlib;
 Andreas> +		i2c->getreg = oc_getreg_grlib;
 Andreas> +	}
 Andreas> +      
 Andreas>  	return 0;
 Andreas>  }
 Andreas>  #else
 Andreas> @@ -311,6 +386,23 @@ static int __devinit ocores_i2c_probe(struct platform_device *pdev)
 Andreas>  	if (i2c->reg_io_width == 0)
 i2c-> reg_io_width = 1; /* Set to default value */
 
 Andreas> +	if (!i2c->getreg) {
 Andreas> +		if (i2c->reg_io_width == 4)
 Andreas> +			i2c->getreg = oc_getreg_32;
 Andreas> +		else if (i2c->reg_io_width == 2)
 Andreas> +			i2c->getreg = oc_getreg_16;
 Andreas> +		else
 Andreas> +			i2c->getreg = oc_getreg_8;
 Andreas> +	}
 Andreas> +	if (!i2c->setreg) {
 Andreas> +		if (i2c->reg_io_width == 4)
 Andreas> +			i2c->setreg = oc_setreg_32;
 Andreas> +		else if (i2c->reg_io_width == 2)
 Andreas> +			i2c->setreg = oc_setreg_16;
 Andreas> +		else
 Andreas> +			i2c->setreg = oc_setreg_8;
 Andreas> +	}
 Andreas> +

These are always set together (could even move to a single ops
structure), so it would be shorter to assign them at the same time:

if (!i2c->setreg || !i2c->getreg) {
   switch (i2c->reg_io_width) {
   case 1:
        i2c->setreg = oc_setreg_8;
        i2c->getreg = oc_getreg_8;
        break;

   case 2:
        i2c->setreg = oc_setreg_16;
        ...

   default:
        dev_err(&pdev->dev "Unsupported I/O width (%d)\n", i2c->reg_io_width);
        return -EINVAL;
   }
}

-- 
Bye, Peter Korsgaard
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