linux-kernel - Re: [PATCH 2/5] USB Kconfig: Select SCSI for USB Mass Storage support

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Date:	Sun, 06 Jan 2008 18:50:43 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Al Boldi <a1426z@...ab.com>
CC:	Sam Ravnborg <sam@...nborg.org>, Adrian Bunk <bunk@...nel.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Brownell <david-b@...bell.net>, Greg KH <greg@...ah.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/5] USB Kconfig: Select SCSI for USB Mass Storage support

Al Boldi wrote:
> Stefan Richter wrote:
>> Al Boldi wrote:
>>>   	menuconfig USB_STORAGE
>>>   	tristate "USB Mass Storage support"
>>> -	depends on USB && SCSI
>>> +	depends on USB && BLOCK
>>> +	select SCSI
>> Still wrong. SCSI also needs HAS_DMA and SCSI_DMA.
> 
> I don't think so.  SCSI selects SCSI_DMA, it doesn't depend on it.

"A selects B" == "A depends on B, but please don't hide A when B is off
and silently switch B on when A is switched on".

config SCSI
	tristate "SCSI device support"
	depends on BLOCK
	select SCSI_DMA if HAS_DMA

So, SCSI doesn't actually need SCSI_DMA per se, but it apparently needs
it whenever HAS_DMA != n.

> So it's safe to select SCSI here, as libata does it the same way.

Sam, does kconfig recursively follow select statements and switch on
options which are select'ed by select'ed options?  I suppose it doesn't.

Maybe this would be better:

 config SCSI
 	tristate "SCSI device support"
 	depends on BLOCK
-	select SCSI_DMA if HAS_DMA

 config SCSI_DMA
 	bool
-	default n
+	default y if SCSI && HAS_DMA

-- 
Stefan Richter
-=====-==--- ---= --==-
http://arcgraph.de/sr/
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