-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 5/5/2013 8:30 PM, Ian McMahon wrote: > What Michael and I had discussed was using the sysfs mechanism to > request the pins at driver load, and only "claim" the pins that > succeed, or fail if a user has asked for pins that we can't claim, > or something along those lines. It's not going to stop code from > going behind our back and manipulating registers directly, but we > just have to assume that we're all playing in the same sandbox.
This seems like a good approach. > What I'm as-yet unsure of is whether we will have a reliable way > to find out whether the onboard peripherals (emmc, hdmi) are > driving the pins they're attached to. - From what I have read, if a "proper" kernel driver is accessing specific SoC pins for something (ie: eMMC or HDMI), attempting to map those ports properly via the kernel (via sysfs or gpio_request() ) will fail, which is the desired behavior. For instance, there is some detail in the BBB manual on disabling the HDMI and MMC drivers if you need access to those I/O pins. Of course, this assumes everyone is "playing by the rules". When I modified the pinmux registers (as root writing directly to the pinmux physical memory locations) to output all PRU I/O to the physical pins, my BB instantly hung, as I broke the SD-card interface. But we should do what we can to "play nice" to avoid such problems, and as a bonus accessing GPIO via the kernel is essentially identical across most ARM SoCs, so the allocation and (slow) access routines can be shared among the BB, Pi, and hopefully whatever else comes along next. - -- Charles Steinkuehler [email protected] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlGHC8QACgkQLywbqEHdNFxRLwCfSn75SEWbRgr3d9ef8sWTSRzC Q/gAoKkzo+kFiWDjD3GmbQWnz7WnZwcw =xMl9 -----END PGP SIGNATURE----- ------------------------------------------------------------------------------ Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
