linux-kernel - Re: chelsio: Use a more common const struct pci_device

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Message-ID: <1424110879.8287.3.camel@perches.com>
Date:	Mon, 16 Feb 2015 10:21:19 -0800
From:	Joe Perches <joe@...ches.com>
To:	Casey Leedom <leedom@...lsio.com>
Cc:	Hariprasad S <hariprasad@...lsio.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	David Miller <davem@...hat.com>
Subject: Re: chelsio: Use a more common const struct pci_device_id foo[]
 style

On Mon, 2015-02-16 at 18:05 +0000, Casey Leedom wrote:
>   I can't quite tell if this is a patch request being sent to
> netdev/David Miller or if it's a suggestion sent to Chelsio that you'd
> like Chelsio to adopt.  I ~think~ it's the latter because the subject
> doesn't include the standard formatting for a patch request but I'm
> not 100% familiar with the netdev/kernel.org conventions for this.  My
> apologies if I'm misinterpreting your message.

Hi Casey.

Nah, that's not it.

I just forgot/neglected to prefix [PATCH] on the email when I
sent it.

The patch touches drivers/net/ethernet and drivers/scsi which
generally means that it's better for the company maintainers
to apply rather than coordinating between David and James,
the linux networking and scsi maintainers.  Those guys for
most part don't like touching each others code areas.

> 1.  The use of "const" certainly seems like a win.

I think so.

My goal here was to make obvious the use of
"const struct pci_device_id" which in the original is very
obfuscated/unclear.

>  2. Thanks for catching the redundant use of CH_PCI_DEVICE_ID_TABLE_DEFINE_BEGIN to guard
>     the actual contents of t4_pci_id_tbl.h.  That's already being handled via the check for
>     __T4_PCI_ID_TBL_H__ — no idea why I put that in there ...

That didn't matter much to me.

>  3. The use of the CH_PCI_DEVICE_ID_TABLE_DEFINE_BEGIN and
>     CH_PCI_DEVICE_ID_TABLE_DEFINE_END are used to make the t4_pci_id_tbl.h
>     accommodate different driver needs.  The header file is only concerned with providing
>     a common enumeration of existing PCI Device Identifiers associated with adapters.
>     The files including the header are only concerned with providing the necessary context
>     for the header file.  The header file ai an OS-independent header file which is
>     shared across six existing OS driver implementations; similar to our OS-independent
>     register definitions file.

I think that OS independent bit is not useful here.

>  4. The CH_PCI_ID_TABLE_ENTRY() macro is similarly used to strictly partition
>     the roles of t4_pci_id_tbl.h and the files which include it.  t4_pci_id_tbl.h is
>     exactly what it's name implies: solely an enumeration of assigned hardware
>     adapter PCI Device Identifiers.

Which is how it's used both before and after this change.

>  5. Because of the above change in the original abstraction layering, a new macro
>     CH_PCI_ID_TABLE_ENTRY_DATA is introduced in this patch which passes in
>     a desired value for the "dev" parameter of the PCI_VDEVICE() macro.  But the
>     documentation for this new macro in t4_pci_id_tbl.h is incorrectly given the
>     documentation of the original CH_PCI_ID_TABLE_ENTRY() macro which
>     was originally supplied by the file including t4_pci_id_tbl.h.  This leaves its
>     usage confusing for anyone reading the header file.

Do you have any clarifying text to suggest?

cheers, Joe

> In conclusion:
> 
>  A. I like the use of "const" in the table.
> 
>  B. I like removing the redundant content inclusion check of
>     CH_PCI_DEVICE_ID_TABLE_DEFINE_BEGIN.
> 
>  C. I'm uncomfortable with all the other changes.

> Casey
> 
> ________________________________________
> From: Joe Perches [joe@...ches.com]
> Sent: Friday, February 13, 2015 6:05 PM
> To: Hariprasad S; Casey Leedom; James E.J. Bottomley
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; linux-scsi
> Subject: chelsio: Use a more common const struct pci_device_id foo[] style
> 
> Chelsio code shares a pci_device_table from an #include file.
> Make the include guard simpler and make the arrays const.
> 
> Reduces data by moving tables to text.
> 
> Removed unnecessary macros:
> o CH_PCI_DEVICE_ID_TABLE_DEFINE_BEGIN
> o CH_PCI_DEVICE_ID_TABLE_DEFINE_END
> o CH_PCI_ID_TABLE_ENTRY (moved to the .h file)
> Added new macro define:
> o CH_PCI_ID_TABLE_ENTRY_DATA
> 
>   text     data     bss     dec     hex filename
>   50550     923     172   51645    c9bd drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.o.new
>   46935    4531     172   51638    c9b6 drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.o.old
>   27864     355       8   28227    6e43 drivers/net/ethernet/chelsio/cxgb4vf/cxgb4vf_main.o.new
>   26072    2203       8   28283    6e7b drivers/net/ethernet/chelsio/cxgb4vf/cxgb4vf_main.o.old
>    9734     450      24   10208    27e0 drivers/scsi/csiostor/csio_init.o.new
>    7942    2242      24   10208    27e0 drivers/scsi/csiostor/csio_init.o.old


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