linux-kernel - Re: ultrastor.c is a bit-rot

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Date:	Mon, 17 Mar 2008 18:00:41 +0200
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	linux-scsi <linux-scsi@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: ultrastor.c is a bit-rot

On Mon, Mar 17 2008 at 17:23 +0200, James Bottomley <James.Bottomley@...senPartnership.com> wrote:
> On Mon, 2008-03-17 at 16:59 +0200, Boaz Harrosh wrote:
>> Inspecting ultrastor.c it is clear to me that this was never used for
>> a loooooooooong time. Not since a PC has more then 2^24 bit of memory.
>> Let me explain below.
>>
>> Now I'm not saying it should be fixed. I'm saying that it should be dumped
>> in the account that it is not used by any one and that it does not work.
>>
>> Why it never worked?
>> ~~~~~~~~~~~~~~~~~~~~~
>>
>> The driver's header says it supports 3 cards
>>
>>  *	14F - ISA first-party DMA HA with floppy support and WD1003 emulation.
>>  *	24F - EISA Bus Master HA with floppy support and WD1003 emulation.
>>  *	34F - VL-Bus Bus Master HA with floppy support (no WD1003 emulation).
>>
>> But Kconfig only specifies ISA. I'm not sure what a VL-Bus is.
> 
> VL is vesa local ... it was an ISA like graphics bus that was fast and
> could reach > 16MB.
> 
>> now the driver defines a static array of structures like this:
>>
>> 	struct {
>> 	  ...
>> 	
>> 	  struct mscp mscp[ULTRASTOR_MAX_CMDS];
>> 	} config = {0};
>>
>> and allocates a struct mscp in .queuecommand like this:
>> 	    my_mscp = &config.mscp[mscp_index];
>>
>> it will go on preparing this my_mscp structure including stuffing
>> some mapped pointers. Lets put that aside for now.
>> At the very end it will pass this my_mscp structure to the card's 
>> firmware like this:
>>
>> 	    /* Store pointer in OGM address bytes */
>> 	outl(isa_virt_to_bus(my_mscp), config.ogm_address);
>>
>> Now this is one hell of a smart ISA card. But putting this aside.
>>
>> if the machine has more then 2^24 of memory. Then this will never
>> work, right? or I'm missing it completely?
> 
> It will definitely work for EISA and VL bus.  I think if you analyse the
> placement of kernel data segments for compiled in drivers, it might also
> work for ISA too, since I think the pfn will be low enough.  It should
> fail as a module not just because the area will be out of range for ISA,
> but also because the module data segment is in vmalloc space, so the
> virt_to_bus assumptions of contiguity could be violated.
> 
> James
> 

So what is the verdict? is it removed? marked broken for ISA?

can I safely say that unchecked_isa_dma can be removed?

Boaz
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