lkml.org 
[lkml]   [2020]   [May]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
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
\
 
 \ /
  Last update: 2020-05-27 16:17    [W:0.068 / U:2.576 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site