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SubjectRe: [PATCH] scsi: use set_host_byte instead of open-coding it
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On 10/10/2017 05:29 PM, Johannes Thumshirn wrote:
> Call set_host_byte() instead of open-coding it.
>
> Converted using this simple Coccinelle spatch
>
> <SmPL>
> @@
> local idexpression struct scsi_cmnd *c;
> expression E1;
> @@
>
> - c->result = E1 << 16;
> + set_host_byte(c, E1);

Maybe I misunderstand, but doesn't set_host_byte only set the host byte
but leave the other 3 parts untouched in c->result?

static inline void set_host_byte(struct scsi_cmnd *cmd, char status)
{
cmd->result = (cmd->result & 0xff00ffff) | (status << 16);
}

In contrast, assigning something to c->result resets all parts.
If so, the semantic patch would introduce a subtle semantic change.
Unless it's guaranteed that in all the touched cases, c->result always
has 0 for status, message, and driver byte before calling set_host_byte().

Bart's suggestion also sounds nice.

FYI: Originally, I only thought about using set_host_byte in that one
place fix of yours; I did not expect a full framework rework.

--
Mit freundlichen Grüßen / Kind regards
Steffen Maier

Linux on z Systems Development

IBM Deutschland Research & Development GmbH
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Geschaeftsfuehrung: Dirk Wittkopp
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