Re: [PATCH 28/57] media: Add ovxxxx_16bit_addr_reg_helpers.h

From: Andy Shevchenko <andy@kernel.org>
To: Hans de Goede <hdegoede@redhat.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Tsuchiya Yuto <kitakar@gmail.com>,
	Yury Luneff <yury.lunev@gmail.com>,
	Nable <nable.maininbox@googlemail.com>,
	andrey.i.trufanov@gmail.com, Fabio Aiuto <fabioaiuto83@gmail.com>,
	linux-media@vger.kernel.org, linux-staging@lists.linux.dev
Subject: Re: [PATCH 28/57] media: Add ovxxxx_16bit_addr_reg_helpers.h
Date: Mon, 23 Jan 2023 20:09:54 +0200	[thread overview]
Message-ID: <Y87NchQIfQ3zah+4@smile.fi.intel.com> (raw)
In-Reply-To: <20230123125205.622152-29-hdegoede@redhat.com>

On Mon, Jan 23, 2023 at 01:51:36PM +0100, Hans de Goede wrote:
> The following drivers under drivers/media/i2c: ov08x40.c, ov13858.c,
> ov13b10.c, ov2680.c, ov2685.c, ov2740.c, ov4689.c, ov5670.c,
> ov5675.c, ov5695.c, ov8856.c, ov9282.c and ov9734.c,
> 
> as well as various "atomisp" sensor drivers in drivers/staging, *all*
> use register access helpers with the following function prototypes:
> 
> int ovxxxx_read_reg(struct ovxxxx_dev *sensor, u16 reg,
>                     unsigned int len, u32 *val);
> 
> int ovxxxx_write_reg(struct ovxxxx_dev *sensor, u16 reg,
>                      unsigned int len, u32 val);
> 
> To read/write registers on Omnivision OVxxxx image sensors wich expect
> a 16 bit register address in big-endian format and which have 1-3 byte
> wide registers, in big-endian format (for the higher width registers).
> 
> Add a new ovxxxx_16bit_addr_reg_helpers.h header file with static inline
> versions of these register access helpers, so that this code duplication
> can be removed.

...

> +#include <asm/unaligned.h>

Usually we put linux/* followed by asm/*.

> +#include <linux/dev_printk.h>
> +#include <linux/i2c.h>
> +
> +static inline int ovxxxx_read_reg(struct i2c_client *client, u16 reg,
> +				  unsigned int len, u32 *val)
> +{
> +	struct i2c_msg msgs[2];

> +	u8 addr_buf[2] = { reg >> 8, reg & 0xff };

Let's use unaligned.h or byteorder/generic.h?

	__be16 addr_buf = cpu_to_be16(reg);

> +	u8 data_buf[4] = { 0, };

0, is not needed.

> +	int ret;
> +
> +	if (len > 4)
> +		return -EINVAL;
> +
> +	msgs[0].addr = client->addr;
> +	msgs[0].flags = 0;
> +	msgs[0].len = ARRAY_SIZE(addr_buf);
> +	msgs[0].buf = addr_buf;

	msgs[0].buf = &addr_buf;

> +	msgs[1].addr = client->addr;
> +	msgs[1].flags = I2C_M_RD;
> +	msgs[1].len = len;

> +	msgs[1].buf = &data_buf[4 - len];

This trick I don't like. Can we have like other driver have it, i.e. switch
case for the possible length and explicit usage of the endian conversion calls?

> +	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
> +	if (ret != ARRAY_SIZE(msgs)) {
> +		dev_err(&client->dev, "read error: reg=0x%4x: %d\n", reg, ret);
> +		return -EIO;
> +	}
> +
> +	*val = get_unaligned_be32(data_buf);
> +
> +	return 0;
> +}
> +
> +#define ovxxxx_read_reg8(s, r, v)	ovxxxx_read_reg(s, r, 1, v)
> +#define ovxxxx_read_reg16(s, r, v)	ovxxxx_read_reg(s, r, 2, v)
> +#define ovxxxx_read_reg24(s, r, v)	ovxxxx_read_reg(s, r, 3, v)
> +
> +static inline int ovxxxx_write_reg(struct i2c_client *client, u16 reg,
> +				   unsigned int len, u32 val)
> +{
> +	u8 buf[6];
> +	int ret;
> +
> +	if (len > 4)
> +		return -EINVAL;

> +	put_unaligned_be16(reg, buf);
> +	put_unaligned_be32(val << (8 * (4 - len)), buf + 2);

Something similar here?

> +	ret = i2c_master_send(client, buf, len + 2);
> +	if (ret != len + 2) {
> +		dev_err(&client->dev, "write error: reg=0x%4x: %d\n", reg, ret);
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
> +#define ovxxxx_write_reg8(s, r, v)	ovxxxx_write_reg(s, r, 1, v)
> +#define ovxxxx_write_reg16(s, r, v)	ovxxxx_write_reg(s, r, 2, v)
> +#define ovxxxx_write_reg24(s, r, v)	ovxxxx_write_reg(s, r, 3, v)
> +
> +static inline int ovxxxx_mod_reg(struct i2c_client *client, u16 reg, u8 mask, u8 val)
> +{
> +	u32 readval;
> +	int ret;
> +
> +	ret = ovxxxx_read_reg8(client, reg, &readval);
> +	if (ret < 0)
> +		return ret;

> +	readval &= ~mask;
> +	val &= mask;
> +	val |= readval;

Usual pattern:

	val = (readval & ~mask) | (val & mask);

> +	return ovxxxx_write_reg8(client, reg, val);
> +}

-- 
With Best Regards,
Andy Shevchenko