From: David Brownell <david-b@pacbell•net>
To: Alan Cox <alan@lxorguk•ukuu.org.uk>
Cc: akpm@osdl•org, Greg KH <gregkh@suse•de>,
linux-usb-devel@lists•sourceforge.net, linuxppc-dev@ozlabs•org
Subject: Re: [linux-usb-devel] [PATCH 1/5] USB: Make usb_hcd_irq work for multi-role USB controllers w/ shared irq
Date: Sat, 24 Nov 2007 09:50:40 -0800 [thread overview]
Message-ID: <200711240950.41235.david-b@pacbell.net> (raw)
In-Reply-To: <20071124170307.773d7317@the-village.bc.nu>
On Saturday 24 November 2007, Alan Cox wrote:
> >
> > What about for platforms where irq 0 is a valid irq?
>
> There are no such platforms. Linus made that absolutely clear every time
> this came up before
>
> 0 - No IRQ
>
> A platform with a physical or bus IRQ of 0 needs to remap it to a
> different constant.
However it's also common practice to use negative numbers to
flag "this is no IRQ" ... avoiding all confusions with zero.
- platform_get_irq(), platform_get_irq_byname() ... never
return zero, they return irq (positive) or errno
- PNP initializes invalid IRQs to "-1", and pnp_check_irq()
handles irq zero as in-range
- I'm sure I've seen negative numbers used elsewhere too
Something like
#define is_valid_irq(x) ((x) >= 0)
would work better than expecting sudden agreement everywhere
about a single number representing "this is not an IRQ".
- Dave
next prev parent reply other threads:[~2007-11-24 17:50 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-24 0:24 [PATCH 0/5] Review request: Cypress c67x00 OTG controller Grant Likely
2007-11-24 0:24 ` [PATCH 1/5] USB: Make usb_hcd_irq work for multi-role USB controllers w/ shared irq Grant Likely
2007-11-24 5:10 ` Greg KH
2007-11-24 17:03 ` [linux-usb-devel] " Alan Cox
2007-11-24 17:15 ` Grant Likely
2007-11-24 17:50 ` David Brownell [this message]
2007-11-24 19:06 ` David Brownell
2007-11-24 19:28 ` Grant Likely
2007-11-24 0:24 ` [PATCH 2/5] USB: Add Cypress c67x00 low level interface code Grant Likely
2007-11-24 19:39 ` David Brownell
2007-11-24 0:24 ` [PATCH 3/5] USB: add Cypress c67x00 OTG controller core driver Grant Likely
2007-11-24 0:24 ` [PATCH 4/5] USB: add Cypress c67x00 OTG controller HCD driver Grant Likely
2007-11-24 3:56 ` [linux-usb-devel] " Alan Stern
2007-11-24 0:24 ` [PATCH 5/5] USB: Add Cypress c67x00 OTG controller driver to Kconfig and Makefiles Grant Likely
2007-11-24 20:12 ` David Brownell
2007-11-24 20:20 ` Grant Likely
2007-11-24 21:03 ` David Brownell
2007-11-24 21:13 ` Grant Likely
2007-11-24 17:57 ` [PATCH 0/5] Review request: Cypress c67x00 OTG controller David Brownell
2007-11-24 19:27 ` Grant Likely
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