Re: Areca RAID driver remaining items?

[erich]

Dear Christoph Hellwig,

I have figure out your comments about "remove internal queueing" and "remove 
odd ioctl".
But about "hardware datastructures", areca's firmware spec is need to get a 
trunk of contingous memory space under 4G.
In 64bit platform arcmsr need to make sure all ccbs have same of 
ccb_phyaddr_hi32 physical address.
If arcmsr use dma_pool_alloc do a separate dma mapping.
Is there any method to avoid ccbs pool cross 4G segment?

- msi should be a module options if at all, but defintitly not
  a config options

In some mainboard if I always enable msi function, it will cause system hang 
up.
If it is not a config option, do you have any idea to avoid this issue?

Best Regards
Erich Chen
----- Original Message ----- 
From: "Christoph Hellwig" <hch@xxxxxxxxxxxxx>
To: "erich" <erich@xxxxxxxxxxxx>
Cc: <linux-scsi@xxxxxxxxxxxxxxx>; <linux-kernel@xxxxxxxxxxxxxxx>; 
<billion.wu@xxxxxxxxxxxx>; <alan@xxxxxxxxxxxxxxxxxxx>; <akpm@xxxxxxxx>; 
<arjan@xxxxxxxxxxxxx>; <oliver@xxxxxxxxxx>
Sent: Wednesday, February 22, 2006 10:57 PM
Subject: Re: Areca RAID driver remaining items?


> On Wed, Feb 22, 2006 at 02:27:32PM +0800, erich wrote:
> > Hi Christoph Hellwig,
> >
> > Thanks for your comment with "arcmsr".
> > I will follow your comment to redo this driver.
> > But I am confuse with your mention about some items.
> > Hope you can tell me more detail and let me realy know your comment.
> >
> >  1- remove internal queueing:
> >
> >      Does the "internal queueing" is mention with arcmsr of ccb_free_list 
> > ?
>
> Currently the drivers queuecommand routine works the following:
>
> 1) perform some checks
> 2) try to post outstanding ccbs
> 3) grab new ccb from freelist and set it up
> 4) try to post new ccb, else enqueue it
>
> there is not poin in having such a pending queue in the driver because
> the midlayer does that work for you.  If ->queuecommand can't immediately
> post a ccb you should return
>
> SCSI_MLQUEUE_HOST_BUSY   if there is a resource shortage at the hba level
> SCSI_MLQUEUE_DEVICE_BUSY if there is a resource shortage at the device 
> level
>
> and the scsi midlayer will try to send the command again once a command
> has been completed on the hba/device.
>
> >  2- fix hardware datastructures:
> >
> >      Does the "fix hardware datastructures" is to fix struct ARCMSR_CDB?
> >      Is it illeagal in linux?
>
> struct CCB is a structure that is passed to the hardware but contains
> pointers which have different sized on different architectures.  This
> is generally very dangerous.  If this is just a cookie that the hardware
> doesn't interpret at all it needs more documentation.  Also the way
> you try to convert from bus to virtual addresses with pACB->vir2phy_offset
> can't work on many linux platforms because the virtual to bus address
> mapping isn't contingous.  you need a separate dma mapping for each ccb,
> a good way to archive that is the dma_pool_ * API.
>
>
> >  3- remove odd ioctls:
> >
> >      How about remove odd ioctl?
>
> generally we don't want to add new ioctls.  For scsi/raid drivers there's
> been an exception where we allow a pass-through to the firmware which
> the managment applications need.  the driver has various ioctls that
> don't seem to fall into that category. 

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