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    Subject[PATCH v2] check: Add 10bit/slave i2c reg flags support
    Date
    Recently the I2C-controllers slave interface support was added to the
    kernel I2C subsystem. In this case Linux can be used as, for example,
    a I2C EEPROM machine. See [1] for details. Other than instantiating
    the EEPROM-slave device from user-space there is a way to declare the
    device in dts. In this case firstly the I2C bus controller must support
    the slave interface. Secondly I2C-slave sub-node of that controller
    must have "reg"-property with flag I2C_OWN_SLAVE_ADDRESS set (flag is
    declared in [2]). That flag is declared as (1 << 30), which when set
    makes dtc unhappy about too big address set for a I2C-slave:

    Warning (i2c_bus_reg): /example-2/i2c@1120000/eeprom@64: I2C bus unit address format error, expected "40000064"
    Warning (i2c_bus_reg): /example-2/i2c@1120000/eeprom@64:reg: I2C address must be less than 10-bits, got "0x40000064"

    Similar problem would have happened if we had set the 10-bit address
    flag I2C_TEN_BIT_ADDRESS in the "reg"-property.

    In order to fix the problem we suggest to alter the I2C-bus reg-check
    algorithm, so one would be aware of the upper bits set. Normally if no
    flag specified, the 7-bit address is expected in the "reg"-property.
    If I2C_TEN_BIT_ADDRESS is set, then the 10-bit address check will be
    performed. The I2C_OWN_SLAVE_ADDRESS flag will be just ignored.

    [1] kernel/Documentation/i2c/slave-interface.rst
    [2] kernel/include/dt-bindings/i2c/i2c.h

    Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
    Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
    Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    Cc: Wolfram Sang <wsa@the-dreams.de>
    Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
    Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
    Cc: Frank Rowand <frowand.list@gmail.com>
    Cc: Rob Herring <robh+dt@kernel.org>
    Cc: devicetree-compiler@vger.kernel.org
    Cc: devicetree@vger.kernel.org
    Cc: linux-i2c@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org

    ---

    Changelog v2:
    - Use unsigned numeric literal in the left-shit operation to avoid UB.
    ---
    checks.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    diff --git a/checks.c b/checks.c
    index 4b3c486f1399..7091d1bc38d2 100644
    --- a/checks.c
    +++ b/checks.c
    @@ -1028,6 +1028,7 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
    const char *unitname = get_unitname(node);
    char unit_addr[17];
    uint32_t reg = 0;
    + uint32_t addr;
    int len;
    cell_t *cells = NULL;

    @@ -1044,17 +1045,21 @@ static void check_i2c_bus_reg(struct check *c, struct dt_info *dti, struct node
    }

    reg = fdt32_to_cpu(*cells);
    - snprintf(unit_addr, sizeof(unit_addr), "%x", reg);
    + addr = reg & 0x3FFFFFFFU;
    + snprintf(unit_addr, sizeof(unit_addr), "%x", addr);
    if (!streq(unitname, unit_addr))
    FAIL(c, dti, node, "I2C bus unit address format error, expected \"%s\"",
    unit_addr);

    for (len = prop->val.len; len > 0; len -= 4) {
    reg = fdt32_to_cpu(*(cells++));
    - if (reg > 0x3ff)
    + addr = reg & 0x3FFFFFFFU;
    + if ((reg & (1U << 31)) && addr > 0x3ff)
    FAIL_PROP(c, dti, node, prop, "I2C address must be less than 10-bits, got \"0x%x\"",
    - reg);
    -
    + addr);
    + else if (!(reg & (1U << 31)) && addr > 0x7f)
    + FAIL_PROP(c, dti, node, prop, "I2C address must be less than 7-bits, got \"0x%x\"",
    + addr);
    }
    }
    WARNING(i2c_bus_reg, check_i2c_bus_reg, NULL, &reg_format, &i2c_bus_bridge);
    --
    2.26.2
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