From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH] check: Add 10bit/slave i2c reg flags support Date: Wed, 27 May 2020 16:36:56 +0300 Message-ID: <20200527133656.GV1634618@smile.fi.intel.com> References: <20200527122525.6929-1-Sergey.Semin@baikalelectronics.ru> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20200527122525.6929-1-Sergey.Semin-UN2wsyeM1qLJ45LvJ/SUn8gurn75+9Lz@public.gmane.org> Sender: devicetree-compiler-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Serge Semin Cc: devicetree-compiler-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Serge Semin , Alexey Malahov , Thomas Bogendoerfer , Wolfram Sang , Jarkko Nikula , Frank Rowand , Rob Herring , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Wed, May 27, 2020 at 03:25:25PM +0300, Serge Semin wrote: > 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 ... > + addr = reg & 0x3FFFFFFFU; > + if ((reg & (1 << 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 & (1 << 31)) && addr > 0x7f) > + FAIL_PROP(c, dti, node, prop, "I2C address must be less than 7-bits, got \"0x%x\"", > + addr); 1 << 31 is UB. -- With Best Regards, Andy Shevchenko