Re: [PATCH v2 1/2] eeprom: at24: convert magic numbers to structs.

[Bartosz Golaszewski <brgl-ARrdPY/1zhM@public.gmane.org>]

2017-12-08 22:25 GMT+01:00 Sven Van Asbroeck <svendev-fuHqz3Nb1YI@public.gmane.org>:
> Fundamental properties such as capacity and page size differ
> among at24-type chips. But these chips do not have an id register,
> so this can't be discovered at runtime.
>
> Traditionally, at24-type eeprom properties were determined in two ways:
> - by passing a 'struct at24_platform_data' via platform_data, or
> - by naming the chip type in the devicetree, which passes a
>         'magic number' to probe(), which is then converted to
>         a 'struct at24_platform_data'.
>
> Recently a bug was discovered because the magic number rounds down

Can you reference the commit here? Use the xxxxxxxxxxxx ("something
something") format.

> all chip sizes to the lowest power of two. This was addressed by
> a work-around, with the wish that magic numbers should over time
> be converted to structs.
>
> This patch replaces the magic numbers with 'struct at24_chip_data'.
>
> Signed-off-by: Sven Van Asbroeck <svendev-fuHqz3Nb1YI@public.gmane.org>
> ---
>  drivers/misc/eeprom/at24.c | 230 ++++++++++++++++++++++-----------------------
>  1 file changed, 110 insertions(+), 120 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 06ffa11..c3759cb 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -105,16 +105,6 @@ struct at24_data {
>  module_param(write_timeout, uint, 0);
>  MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
>
> -#define AT24_SIZE_BYTELEN 5
> -#define AT24_SIZE_FLAGS 8
> -
> -#define AT24_BITMASK(x) (BIT(x) - 1)
> -
> -/* create non-zero magic value for given eeprom parameters */
> -#define AT24_DEVICE_MAGIC(_len, _flags)                \
> -       ((1 << AT24_SIZE_FLAGS | (_flags))              \
> -           << AT24_SIZE_BYTELEN | ilog2(_len))
> -
>  /*
>   * Both reads and writes fail if the previous write didn't complete yet. This
>   * macro loops a few times waiting at least long enough for one entire page
> @@ -131,113 +121,119 @@ struct at24_data {
>              op_time ? time_before(op_time, tout) : true;               \
>              usleep_range(1000, 1500), op_time = jiffies)
>
> +struct at24_chip_data {
> +       /*
> +        * these fields mirror their equivalents in
> +        * struct at24_platform_data
> +        */
> +       u32 byte_len;
> +       u8 flags;
> +};
> +
> +#define AT24_CHIP_DATA(_name, _len, _flags) \

Move the backslash to the end of the line as is done in other macros
in this file. Same applies below.

> +       static const struct at24_chip_data at24_data_##_name = { \
> +               .byte_len = _len, .flags = _flags, \
> +       }
> +
> +#define AT24_I2C_DEVICE_ID(_name) \
> +       { #_name, (kernel_ulong_t)&at24_data_##_name }
> +
> +#define AT24_ACPI_DEVICE_ID(_name) \
> +       { #_name, (kernel_ulong_t)&at24_data_##_name }
> +
> +#define AT24_OF_DEVICE_ID(_of_compat, _name) \
> +       { .compatible = _of_compat, .data = &at24_data_##_name }
> +
> +/* needs 8 addresses as A0-A2 are ignored */
> +AT24_CHIP_DATA(24c00, 128 / 8, AT24_FLAG_TAKE8ADDR);
> +/* old variants can't be handled with this generic entry! */
> +AT24_CHIP_DATA(24c01, 1024 / 8, 0);
> +AT24_CHIP_DATA(24cs01, 16, AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
> +AT24_CHIP_DATA(24c02, 2048 / 8,        0);
> +AT24_CHIP_DATA(24cs02, 16, AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
> +AT24_CHIP_DATA(24mac402, 48 / 8,
> +       AT24_FLAG_MAC | AT24_FLAG_READONLY);

Why are you breaking the line here if it fits fine within the 80
characters limit?

> +AT24_CHIP_DATA(24mac602, 64 / 8,
> +       AT24_FLAG_MAC | AT24_FLAG_READONLY);
> +/* spd is a 24c02 in memory DIMMs */
> +AT24_CHIP_DATA(spd, 2048 / 8,
> +       AT24_FLAG_READONLY | AT24_FLAG_IRUGO);
> +AT24_CHIP_DATA(24c04, 4096 / 8,        0);
> +AT24_CHIP_DATA(24cs04, 16,
> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
> +/* 24rf08 quirk is handled at i2c-core */
> +AT24_CHIP_DATA(24c08, 8192 / 8,        0);
> +AT24_CHIP_DATA(24cs08, 16,
> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
> +AT24_CHIP_DATA(24c16, 16384 / 8, 0);
> +AT24_CHIP_DATA(24cs16, 16,
> +       AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
> +AT24_CHIP_DATA(24c32, 32768 / 8,       AT24_FLAG_ADDR16);
> +AT24_CHIP_DATA(24cs32, 16,
> +       AT24_FLAG_ADDR16 |
> +       AT24_FLAG_SERIAL |
> +       AT24_FLAG_READONLY);

All the flags fit nicely in a single line, so don't be to eager to break them.

> +AT24_CHIP_DATA(24c64, 65536 / 8,       AT24_FLAG_ADDR16);
> +AT24_CHIP_DATA(24cs64, 16,
> +       AT24_FLAG_ADDR16 |
> +       AT24_FLAG_SERIAL |
> +       AT24_FLAG_READONLY);
> +AT24_CHIP_DATA(24c128, 131072 / 8,     AT24_FLAG_ADDR16);
> +AT24_CHIP_DATA(24c256, 262144 / 8,     AT24_FLAG_ADDR16);
> +AT24_CHIP_DATA(24c512, 524288 / 8,     AT24_FLAG_ADDR16);
> +AT24_CHIP_DATA(24c1024, 1048576 / 8,   AT24_FLAG_ADDR16);
> +/* identical to 24c08 ? */
> +AT24_CHIP_DATA(INT3499, 8192 / 8, 0);
> +
>  static const struct i2c_device_id at24_ids[] = {
> -       /* needs 8 addresses as A0-A2 are ignored */
> -       { "24c00",      AT24_DEVICE_MAGIC(128 / 8,      AT24_FLAG_TAKE8ADDR) },
> -       /* old variants can't be handled with this generic entry! */
> -       { "24c01",      AT24_DEVICE_MAGIC(1024 / 8,     0) },
> -       { "24cs01",     AT24_DEVICE_MAGIC(16,
> -                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
> -       { "24c02",      AT24_DEVICE_MAGIC(2048 / 8,     0) },
> -       { "24cs02",     AT24_DEVICE_MAGIC(16,
> -                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
> -       { "24mac402",   AT24_DEVICE_MAGIC(48 / 8,
> -                               AT24_FLAG_MAC | AT24_FLAG_READONLY) },
> -       { "24mac602",   AT24_DEVICE_MAGIC(64 / 8,
> -                               AT24_FLAG_MAC | AT24_FLAG_READONLY) },
> -       /* spd is a 24c02 in memory DIMMs */
> -       { "spd",        AT24_DEVICE_MAGIC(2048 / 8,
> -                               AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
> -       { "24c04",      AT24_DEVICE_MAGIC(4096 / 8,     0) },
> -       { "24cs04",     AT24_DEVICE_MAGIC(16,
> -                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
> -       /* 24rf08 quirk is handled at i2c-core */
> -       { "24c08",      AT24_DEVICE_MAGIC(8192 / 8,     0) },
> -       { "24cs08",     AT24_DEVICE_MAGIC(16,
> -                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
> -       { "24c16",      AT24_DEVICE_MAGIC(16384 / 8,    0) },
> -       { "24cs16",     AT24_DEVICE_MAGIC(16,
> -                               AT24_FLAG_SERIAL | AT24_FLAG_READONLY) },
> -       { "24c32",      AT24_DEVICE_MAGIC(32768 / 8,    AT24_FLAG_ADDR16) },
> -       { "24cs32",     AT24_DEVICE_MAGIC(16,
> -                               AT24_FLAG_ADDR16 |
> -                               AT24_FLAG_SERIAL |
> -                               AT24_FLAG_READONLY) },
> -       { "24c64",      AT24_DEVICE_MAGIC(65536 / 8,    AT24_FLAG_ADDR16) },
> -       { "24cs64",     AT24_DEVICE_MAGIC(16,
> -                               AT24_FLAG_ADDR16 |
> -                               AT24_FLAG_SERIAL |
> -                               AT24_FLAG_READONLY) },
> -       { "24c128",     AT24_DEVICE_MAGIC(131072 / 8,   AT24_FLAG_ADDR16) },
> -       { "24c256",     AT24_DEVICE_MAGIC(262144 / 8,   AT24_FLAG_ADDR16) },
> -       { "24c512",     AT24_DEVICE_MAGIC(524288 / 8,   AT24_FLAG_ADDR16) },
> -       { "24c1024",    AT24_DEVICE_MAGIC(1048576 / 8,  AT24_FLAG_ADDR16) },
> +       AT24_I2C_DEVICE_ID(24c00),
> +       AT24_I2C_DEVICE_ID(24c01),
> +       AT24_I2C_DEVICE_ID(24cs01),
> +       AT24_I2C_DEVICE_ID(24c02),
> +       AT24_I2C_DEVICE_ID(24cs02),
> +       AT24_I2C_DEVICE_ID(24mac402),
> +       AT24_I2C_DEVICE_ID(24mac602),
> +       AT24_I2C_DEVICE_ID(spd),
> +       AT24_I2C_DEVICE_ID(24c04),
> +       AT24_I2C_DEVICE_ID(24cs04),
> +       AT24_I2C_DEVICE_ID(24c08),
> +       AT24_I2C_DEVICE_ID(24cs08),
> +       AT24_I2C_DEVICE_ID(24c16),
> +       AT24_I2C_DEVICE_ID(24cs16),
> +       AT24_I2C_DEVICE_ID(24c32),
> +       AT24_I2C_DEVICE_ID(24cs32),
> +       AT24_I2C_DEVICE_ID(24c64),
> +       AT24_I2C_DEVICE_ID(24cs64),
> +       AT24_I2C_DEVICE_ID(24c128),
> +       AT24_I2C_DEVICE_ID(24c256),
> +       AT24_I2C_DEVICE_ID(24c512),
> +       AT24_I2C_DEVICE_ID(24c1024),

I missed that before, but we use strings which can be found in the
device tree and sysfs here and we may want to grep for them too.
Please make these macros similar to the of ones and have the names
explicitly in the source code. The same applies for the single chip
defined in the ACPI table.

>         { "at24", 0 },
>         { /* END OF LIST */ }
>  };
>  MODULE_DEVICE_TABLE(i2c, at24_ids);
>
>  static const struct of_device_id at24_of_match[] = {
> -       {
> -               .compatible = "atmel,24c00",
> -               .data = (void *)AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR)
> -       },
> -       {
> -               .compatible = "atmel,24c01",
> -               .data = (void *)AT24_DEVICE_MAGIC(1024 / 8, 0)
> -       },
> -       {
> -               .compatible = "atmel,24c02",
> -               .data = (void *)AT24_DEVICE_MAGIC(2048 / 8, 0)
> -       },
> -       {
> -               .compatible = "atmel,spd",
> -               .data = (void *)AT24_DEVICE_MAGIC(2048 / 8,
> -                               AT24_FLAG_READONLY | AT24_FLAG_IRUGO)
> -       },
> -       {
> -               .compatible = "atmel,24c04",
> -               .data = (void *)AT24_DEVICE_MAGIC(4096 / 8, 0)
> -       },
> -       {
> -               .compatible = "atmel,24c08",
> -               .data = (void *)AT24_DEVICE_MAGIC(8192 / 8, 0)
> -       },
> -       {
> -               .compatible = "atmel,24c16",
> -               .data = (void *)AT24_DEVICE_MAGIC(16384 / 8, 0)
> -       },
> -       {
> -               .compatible = "atmel,24c32",
> -               .data = (void *)AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16)
> -       },
> -       {
> -               .compatible = "atmel,24c64",
> -               .data = (void *)AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16)
> -       },
> -       {
> -               .compatible = "atmel,24c128",
> -               .data = (void *)AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16)
> -       },
> -       {
> -               .compatible = "atmel,24c256",
> -               .data = (void *)AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16)
> -       },
> -       {
> -               .compatible = "atmel,24c512",
> -               .data = (void *)AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16)
> -       },
> -       {
> -               .compatible = "atmel,24c1024",
> -               .data = (void *)AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16)
> -       },
> -       { },
> +       AT24_OF_DEVICE_ID("atmel,24c00", 24c00),
> +       AT24_OF_DEVICE_ID("atmel,24c01", 24c01),
> +       AT24_OF_DEVICE_ID("atmel,24c02", 24c02),
> +       AT24_OF_DEVICE_ID("atmel,spd", spd),
> +       AT24_OF_DEVICE_ID("atmel,24c04", 24c04),
> +       AT24_OF_DEVICE_ID("atmel,24c08", 24c08),
> +       AT24_OF_DEVICE_ID("atmel,24c16", 24c16),
> +       AT24_OF_DEVICE_ID("atmel,24c32", 24c32),
> +       AT24_OF_DEVICE_ID("atmel,24c64", 24c64),
> +       AT24_OF_DEVICE_ID("atmel,24c128", 24c128),
> +       AT24_OF_DEVICE_ID("atmel,24c256", 24c256),
> +       AT24_OF_DEVICE_ID("atmel,24c512", 24c512),
> +       AT24_OF_DEVICE_ID("atmel,24c1024", 24c1024),
> +       { /* END OF LIST */ },
>  };
>  MODULE_DEVICE_TABLE(of, at24_of_match);
>
>  static const struct acpi_device_id at24_acpi_ids[] = {
> -       { "INT3499", AT24_DEVICE_MAGIC(8192 / 8, 0) },
> -       { }
> +       AT24_ACPI_DEVICE_ID(INT3499),
> +       { /* END OF LIST */ }
>  };
>  MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
>
> @@ -525,8 +521,8 @@ static unsigned int at24_get_offset_adj(u8 flags, unsigned int byte_len)
>
>  static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>  {
> -       struct at24_platform_data chip;
> -       kernel_ulong_t magic = 0;
> +       struct at24_platform_data chip = { 0 };
> +       const struct at24_chip_data *cd = NULL;
>         bool writable;
>         struct at24_data *at24;
>         int err;
> @@ -544,28 +540,22 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
>                  */
>                 if (client->dev.of_node &&
>                     of_match_device(at24_of_match, &client->dev)) {
> -                       magic = (kernel_ulong_t)
> -                               of_device_get_match_data(&client->dev);
> +                       cd = of_device_get_match_data(&client->dev);
>                 } else if (id) {
> -                       magic = id->driver_data;
> +                       cd = (void *)id->driver_data;
>                 } else {
>                         const struct acpi_device_id *aid;
>
>                         aid = acpi_match_device(at24_acpi_ids, &client->dev);
>                         if (aid)
> -                               magic = aid->driver_data;
> +                               cd = (void *)aid->driver_data;
>                 }
> -               if (!magic)
> +               if (!cd)
>                         return -ENODEV;
>
> -               chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
> -               magic >>= AT24_SIZE_BYTELEN;
> -               chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
> -
> +               chip.byte_len = cd->byte_len;
> +               chip.flags = cd->flags;
>                 at24_get_pdata(&client->dev, &chip);
> -
> -               chip.setup = NULL;
> -               chip.context = NULL;
>         }
>
>         if (!is_power_of_2(chip.byte_len))
> --
> 1.9.1
>

Thanks,
Bartosz
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