Date: Thu, 19 Jun 2014 09:19:04 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org Cc: Emeric POUPON <emeric.poupon@arkoon-netasq.com> Subject: Re: How to properly handle several fonctions provided by the Winbond SuperIO chip? Message-ID: <201406190919.04443.jhb@freebsd.org> In-Reply-To: <1118241087.138096.1403180509132.JavaMail.zimbra@arkoon-netasq.com> References: <1118241087.138096.1403180509132.JavaMail.zimbra@arkoon-netasq.com>
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On Thursday, June 19, 2014 8:21:49 am Emeric POUPON wrote: > 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? This sounds correct to treat the raw device as a bus and the logical devices it provides as children. -- John Baldwin
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