linux-kernel - Re: [PATCH v8 2/7] scsi: libsas: Define NCQ Priority sysfs attributes for SATA devices

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Date: Tue, 26 Mar 2024 10:53:30 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Igor Pylypiv <ipylypiv@...gle.com>
Cc: Damien Le Moal <dlemoal@...nel.org>, Niklas Cassel <cassel@...nel.org>, 
	John Garry <john.g.garry@...cle.com>, Jason Yan <yanaijie@...wei.com>, 
	"James E.J. Bottomley" <jejb@...ux.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	Jack Wang <jinpu.wang@...ud.ionos.com>, Hannes Reinecke <hare@...e.de>, 
	Xiang Chen <chenxiang66@...ilicon.com>, Artur Paszkiewicz <artur.paszkiewicz@...el.com>, 
	Bart Van Assche <bvanassche@....org>, TJ Adams <tadamsjr@...gle.com>, linux-ide@...r.kernel.org, 
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 2/7] scsi: libsas: Define NCQ Priority sysfs attributes
 for SATA devices

Hi Igor,

On Thu, Mar 7, 2024 at 10:55 PM Igor Pylypiv <ipylypiv@...gle.com> wrote:
> Libata sysfs attributes cannot be used for libsas managed SATA devices
> because the ata_port location is different for libsas.
>
> Defined sysfs attributes (visible for SATA devices only):
> - /sys/block/sda/device/ncq_prio_enable
> - /sys/block/sda/device/ncq_prio_supported
>
> The newly defined attributes will pass the correct ata_port to libata
> helper functions.
>
> Reviewed-by: John Garry <john.g.garry@...cle.com>
> Reviewed-by: Damien Le Moal <dlemoal@...nel.org>
> Reviewed-by: Jason Yan <yanaijie@...wei.com>
> Signed-off-by: Igor Pylypiv <ipylypiv@...gle.com>

Thanks for your patch, which is now commit b4d3ddd2df7531e3 ("scsi:
libsas: Define NCQ Priority sysfs attributes for SATA devices")
in scsi-mkp/for-next

> --- a/drivers/scsi/libsas/sas_ata.c
> +++ b/drivers/scsi/libsas/sas_ata.c

> +
> +DEVICE_ATTR(ncq_prio_supported, S_IRUGO, sas_ncq_prio_supported_show, NULL);
> +

[...]

> +
> +DEVICE_ATTR(ncq_prio_enable, S_IRUGO | S_IWUSR,
> +           sas_ncq_prio_enable_show, sas_ncq_prio_enable_store);
> +

When both CONFIG_SCSI_SAS_ATA and CONFIG_SATA_HOST are enabled:

aarch64-linux-gnu-ld: drivers/ata/libata-sata.o:(.data+0x110):
multiple definition of `dev_attr_ncq_prio_supported';
drivers/scsi/libsas/sas_ata.o:(.data+0x260): first defined here
aarch64-linux-gnu-ld: drivers/ata/libata-sata.o:(.data+0xd8): multiple
definition of `dev_attr_ncq_prio_enable';
drivers/scsi/libsas/sas_ata.o:(.data+0x228): first defined here

Making both new DEVICE_ATTR() declarations static doesn't work,
as <linux/libata.h> contains a forward declaration for the existing global
dev_attr_ncq_prio_supported in libata:

In file included from include/linux/async.h:14,
                 from drivers/scsi/libsas/sas_ata.c:12:
include/linux/device.h:156:33: error: static declaration of
‘dev_attr_ncq_prio_supported’ follows non-static declaration
  156 |         struct device_attribute dev_attr_##_name =
__ATTR(_name, _mode, _show, _store)
      |                                 ^~~~~~~~~
drivers/scsi/libsas/sas_ata.c:984:8: note: in expansion of macro ‘DEVICE_ATTR’
  984 | static DEVICE_ATTR(ncq_prio_supported, S_IRUGO,
sas_ncq_prio_supported_show,
      |        ^~~~~~~~~~~
In file included from include/scsi/sas_ata.h:13,
                 from drivers/scsi/libsas/sas_ata.c:15:
include/linux/libata.h:508:32: note: previous declaration of
‘dev_attr_ncq_prio_supported’ with type ‘struct device_attribute’
  508 | extern struct device_attribute dev_attr_ncq_prio_supported;
      |                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from include/linux/async.h:14,
                 from drivers/scsi/libsas/sas_ata.c:12:
include/linux/device.h:156:33: error: static declaration of
‘dev_attr_ncq_prio_enable’ follows non-static declaration
  156 |         struct device_attribute dev_attr_##_name =
__ATTR(_name, _mode, _show, _store)
      |                                 ^~~~~~~~~
drivers/scsi/libsas/sas_ata.c:1023:8: note: in expansion of macro ‘DEVICE_ATTR’
 1023 | static DEVICE_ATTR(ncq_prio_enable, S_IRUGO | S_IWUSR,
      |        ^~~~~~~~~~~
In file included from include/scsi/sas_ata.h:13,
                 from drivers/scsi/libsas/sas_ata.c:15:
include/linux/libata.h:509:32: note: previous declaration of
‘dev_attr_ncq_prio_enable’ with type ‘struct device_attribute’
  509 | extern struct device_attribute dev_attr_ncq_prio_enable;
      |                                ^~~~~~~~~~~~~~~~~~~~~~~~

Perhaps the new attributes can be renamed?
Alternatively, the DEVICE_ATTR() can be open-coded, so the actual
device_attribute structures are named differently.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds