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Date: Tue, 9 Nov 2010 22:04:25 +0900 From: Simon Horman <horms@...ge.net.au> To: linux-kernel@...r.kernel.org Cc: Anton Vorontsov <avorontsov@...mvista.com>, David Brownell <dbrownell@...rs.sourceforge.net> Subject: gpiolib: Questions about gpiochip_find_base() Hi, I have a few questions about gpiochip_find_base() which I hope someone can help with. * At the end of gpiochip_add() there is the following code: if (gpio_is_valid(base)) pr_debug("%s: found new base at %d\n", __func__, base); return base; It is unclear to me why !gpio_is_valid(base) isn't an error condition given that the following appears in gpiochip_add(), the caller of gpiochip_find_base(), in the case where base isn't to be dynamic selected. if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1)) && base >= 0) { status = -EINVAL; goto fail; } * In the same vein, its unclear to me why the loop in gpiochip_find_base() checks values of i that may not be valid according to gpio_is_valid(). Specifically I am wondering why for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) { ... if (!chip && !test_bit(FLAG_RESERVED, &desc->flags)) { ... isn't something like for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) { ... if (gpio_is_valid(i) && !chip && !test_bit(FLAG_RESERVED, &desc->flags)) { ... * I am wondering if in gpiochip_add() the following is unnecessary in the case where base is dynamic as gpiochip_add() seems to ensure that gpio_desc[id].chip is NULL for the dynamically selected range. for (id = base; id < base + chip->ngpio; id++) { if (gpio_desc[id].chip != NULL) { status = -EBUSY; break; } } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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