On 16/10/12 10:31, Roland Stigge wrote: > The recurring task of providing simultaneous access to GPIO lines (especially > for bit banging protocols) needs an appropriate API. > > This patch adds a kernel internal "Block GPIO" API that enables simultaneous > access to several GPIOs. This is done by abstracting GPIOs to an n-bit word: > Once requested, it provides access to a group of GPIOs which can range over > multiple GPIO chips. > > Signed-off-by: Roland Stigge <sti...@antcom.de> > ---
<snip> > +This creates a new block of GPIOs as a list of GPIO numbers with the > specified > +size which are accessible via the returned struct gpio_block and the accessor > +functions described below. Please note that you need to request the GPIOs > +separately via gpio_request(). An arbitrary list of globally valid GPIOs can > be > +specified, even ranging over several gpio_chips. Actual handling of I/O > +operations will be done on a best effort base, i.e. simultaneous I/O only > where > +possible by hardware and implemented in the respective GPIO driver. The > number > +of GPIOs in one block is limited to 32 on a 32 bit system, and 64 on a 64 bit > +system. However, several blocks can be defined at once. This should probably say that the number of gpios in a block is limited to sizeof(unsigned long) or BITS_PER_LONG. I think sizeof(unsigned long) == 8 on some 32 bit architectures. ~Ryan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
