> -----Original Message----- > From: Dmitry Torokhov [mailto:dmitry.torokhov@xxxxxxxxx] > Sent: Saturday, February 27, 2010 2:30 PM > To: Govindarajan, Sriramakrishnan > Cc: Felipe Balbi; linux-omap@xxxxxxxxxxxxxxx; linux-input@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/3] TCA6416 keypad : Implement keypad driver for keys > interfaced to TCA6416 ---snip--- > > > > I see, > > > > > > > > shouldn't you instead provide a gpiolib driver for tca6416 and use > the > > > > generic gpio_keys driver ?? > > > > > > > > > > Right. The fact that the driver precludes all otehr gpios from being > > > used is a major drawback. > > > [Sriram] gpio_keys implementation assumes that every key can generate > > an interrupt to the processor and also the state machine to process > > events will handle each line individually. Imagine if 16 keys are > > connected to the TCA controller and you have to query(assume it is > > polling, interrupt mode not possible - as you have single interrupt > > line to the processor for event on any of the 16 input lines) 16 lines > > individually over i2c bus - the associated overhead is too high. > > Instead this implementation handles the necessary book-keeping in one > > simple function (get status of all 16 lines in one read transaction). > > Building on a GPIO implementation and using gpio-keys above will be > > both clumsy and incur runtime overhead as against a direct keypad > > driver. > > > > More often(as on AM3517EVM) the keypad keys are not mixed with other > > GPIO keys. The initial implementation includes key_mask to identify > > the keys to be used for keypad and the others are logically not > > modified. Hence the implementation can be extended if need arises to > > overcome this restriction. > > In this case you should not build on gpio_keys at all but select some > other keyboard as an example that smply uses keytable with set of > keycodes, single interrupt, etc. The overhead of all gpio_keys data > structures is not needed here. > [Sriram] I am working on cleaning up the driver to use a simpler book keeping structure(move away from gpio_keys). Will post the reworked patch shortly. ---snip --- > > > [Sriram] All the core logic (including I2C transactions) is > > implemented through a work queue implementation. The ISR is slim and > > only schedules the work queue. This also enables the implementation to > > be easily adaptable for both interrupt/polled mode. > > > > Fair enough but you need to ensure that you do not leave irq unbalances > (in regards to enable/disable) when you using workqueue and disabling > interrupt in the ISR. [Sriram] Will ensure that this is addressed appropriately (including cleanup on error conditions). --- Sriram -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
