Re: [parisc-linux] How retrieving HPA/SPA with the device node

[Bruno Vidal <bruno_vidal@hpfrcu03.france.hp.com>]

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	Hi
I've finally found enought time to continu my long way to the HPA.
So now I've build a function in sd.c in order to retrieve the scsi_host.
But as it has been said, the pointer pci_dev in the structure scsi_host
is not always pointing to a pci_dev. For my poor 712/100, it point
to NULL :-( (it is normal, my scsi host is not a PCI one). So I'm still
stuck at this point, now I'm able to retrieve the scsi_host and scsi_dev
structures, but I'm still unable to go the parisc_device. Any idea ?

	Thanks.

Grant Grundler wrote:
> 
> Bruno Vidal wrote:
> > The pointer of the disk (/dev/sd??) is the node. Example:
> > /dev/sda2 ->> sda2 -> 0x802 -> major:0x8 -> driver "sd" with minor:0x02
> > Now how can I link 0x802 to hardware path "2/0/1"
> > So where is the link between both ????? Do you have any idea ?????
> 
> Well, there is a link. It's just not as obvious as the iotree.
> 
> drivers/scsi/sd.c:sd_open() finds the device:
> 
>         target = DEVICE_NR(inode->i_rdev);
>         if (target >= sd_template.dev_max || !rscsi_disks[target].device)
>                 return -ENXIO;  /* No such device */
> 
> And sd.h has the definition for Scsi_Disk:
> typedef struct scsi_disk {
>         unsigned capacity;      /* size in blocks */
>         Scsi_Device *device;
>         unsigned char ready;    /* flag ready for FLOPTICAL */
>         unsigned char write_prot;       /* flag write_protect for rmvable dev */
>         unsigned char sector_bit_size;  /* sector_size = 2 to the  bit size power */
>         unsigned char sector_bit_shift;         /* power of 2 sectors per FS block */
>         unsigned has_part_table:1;      /* has partition table */
> } Scsi_Disk;
> 
> Scsi_Device is *private*. It contains the ptr to Scsi_Host (defined
> in hosts.h), an instance of a SCSI controller driver. And finally,
> Scsi_Host has a pointer to pci_dev.
> 
> Since several of the data structures are intended to be private,
> I suggest adding a function to sd.c (or scsi.c) that finds and returns
> the pci_dev pointer:
> 
> struct pci_dev *sd_get_pci_dev(struct inode *inode)
> {
>         int target = DEVICE_NR(inode->i_rdev);
>         Scsi_Device scsidev = rscsi_disks[target].device;
> 
>         if (target >= sd_template.dev_max || !scsidev)
>                 return NULL;  /* No such device */
> 
>         return (scsi_dev->host->pci_dev);
> }
> 
> It would be nice if SCSI were part of the IO tree but I can understand
> reasons for not doing it. In particular, SCSI over FC doesn't lend
> itself to an IO Tree arrangement since it's really a "net". Put a SAN,
> additional FC controllers from the same host, and a few thousand
> LUNs out there and the IO tree can become an ugly mess to.
> 
> hth,
> grant
> 
> ps. I had no clue how this worked until I tracked this down starting
>     at sd_open().
> 
> _______________________________________________
> parisc-linux mailing list
> parisc-linux@lists.parisc-linux.org
> http://lists.parisc-linux.org/mailman/listinfo/parisc-linux

-- 
	Vidal Bruno, (770-4271)
        SSD-HA Team, HP-UX & LINUX Support
	bruno_vidal@admin.france.hp.com

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