From mboxrd@z Thu Jan 1 00:00:00 1970 From: Holger Schurig Subject: Re: Auto-detecting touchscreen controller and dealing with hw configuration differences on q8 tablets Date: Mon, 20 Jun 2016 12:33:57 +0200 Message-ID: <87r3bsywru.fsf@gmail.com> References: <5E70AD96-4E8E-4430-AF99-0AA0FCF5F8E7@konsulko.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5E70AD96-4E8E-4430-AF99-0AA0FCF5F8E7@konsulko.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Pantelis Antoniou , Hans de Goede Cc: devicetree@vger.kernel.org, linux-sunxi , Jelle van der Waa , "u-boot@lists.denx.de" , Chen-Yu Tsai , Maxime Ripard , linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org > u-boot will work, but you will get into trouble if you demand users to drop to u-boot > to make changes. On my device I use barebox, which is a bit easier *) to use than U-Boot. Still I don't expect my users to the bootloader. Instead my hardware has a 256 byte i2c EEPROM where I store information. And the user can run a user-space command to change settings there, e.g. uccomm verbose_boot yes uccomm power_config ignition ... and so on. I could do some of them via bootloader environment files, but not all. And this is the other obvious way of doing "communication" from Linux user-space to bootloader: setting the environment. The bootloader could mount the partition and try to source some file, to get the info needed. *) in barebox, you have actual shell-like script that look sane, not variables that call variables, e.g. you can do things like this: if [ $oem_id = 255 ]; then splash -x 550 -y 500 -b 0xffffff /env/logo.png fb0.enable=1 pwm_02080000.period_ns=200000 pwm_02080000.duty_ns=160000 pwm_02080000.enable=1 fi gpio_set_value 191 1 There are also commands available to directly modify the device tree.