Date: Thu, 19 Jun 2014 14:21:49 +0200 (CEST) From: Emeric POUPON <emeric.poupon@arkoon-netasq.com> To: freebsd-arch@freebsd.org Subject: How to properly handle several fonctions provided by the Winbond SuperIO chip? Message-ID: <1118241087.138096.1403180509132.JavaMail.zimbra@arkoon-netasq.com> In-Reply-To: <961817567.135121.1403178816482.JavaMail.zimbra@arkoon-netasq.com>
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Hello, I have a design question about how to configure/control a Winbond Super IO device. Currently, only the Watchdog feature is properly handled in FreeBSD (see dev/wbwd), but I would like to control the GPIO that are managed by this SuperIO device. Making a complete separate isa driver seems not to be a good idea : - duplicated probe/attach routines. - concurrency accesses on the registers. Indeed this device provides an "extended mode" in order to be configured, and it also provides a "logical device" selection in order to access specific features (one logical device for the watchdog, another one for a GPIO port, etc.). As far as I understand, they solved the problem on Linux by : - using separate drivers - using a memory locked mechanism when entering/exiting the extended mode. However, on FreeBSD I would split the whole thing in three drivers: - wbsio (sio stands for SuperIO), the main driver: - identify/attach/probe routines on the isa bus. - provide primitives to enter/exit the extended mode, and hangle an internal mutex to give exclusive access on this mode. - provide primitives to select the logical device and read/write the internal registers - attach child devices "wbwd" and "gpio". - wbwd, - child of wbsio - register the watchdog event callback - use wbsio primitives to get the work done - wbgpio, - child of wbsio - implement gpio methods - add child devices "gpioc" and "gpiobus" - use wbsio primitives to get the work done What do you think? Is that the good way to proceed? Regards, Emeric POUPON
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