linux-kernel - Re: [PATCH v4 6/7] firmware/efi: Process CXL Component Events

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Date: Tue, 19 Dec 2023 07:43:45 -0800
From: Ira Weiny <ira.weiny@...el.com>
To: Dan Williams <dan.j.williams@...el.com>, Smita Koralahalli
	<Smita.KoralahalliChannabasappa@....com>, Ira Weiny <ira.weiny@...el.com>,
	Jonathan Cameron <jonathan.cameron@...wei.com>, Shiju Jose
	<shiju.jose@...wei.com>
CC: Yazen Ghannam <yazen.ghannam@....com>, Davidlohr Bueso
	<dave@...olabs.net>, Dave Jiang <dave.jiang@...el.com>, Alison Schofield
	<alison.schofield@...el.com>, Vishal Verma <vishal.l.verma@...el.com>, "Ard
 Biesheuvel" <ardb@...nel.org>, <linux-efi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>
Subject: Re: [PATCH v4 6/7] firmware/efi: Process CXL Component Events

Dan Williams wrote:
> Smita Koralahalli wrote:
> > On 12/15/2023 3:26 PM, Ira Weiny wrote:

[snip]

> > > +	struct {
> > > +		u32 length;
> > > +		u64 validation_bits;
> > > +		struct cper_cxl_event_devid {
> > > +			u16 vendor_id;
> > > +			u16 device_id;
> > > +			u8 func_num;
> > > +			u8 device_num;
> > > +			u8 bus_num;
> > > +			u16 segment_num;
> > > +			u16 slot_num; /* bits 2:0 reserved */
> > > +			u8 reserved;
> > > +		} device_id __packed;
> > > +		struct cper_cxl_event_sn {
> > > +			u32 lower_dw;
> > > +			u32 upper_dw;
> > > +		} dev_serial_num __packed;
> > > +	} hdr __packed;
> > > +
> > > +	union cxl_event event;
> > > +} __packed;
> > > +
> > 
> > For some reason, prefixing the struct name with __packed attribute seems 
> > to do the job. ("__packed device_id" and "__packed dev_serial_num").
> 
> Good catch, yeah, the expectation is that follows the closing brace not
> only to match the predominant style in the kernel, but gcc appears to
> not honor it otherwise. Looks better with this on top:

Very good catch.  I did not mean to do this at all...  :-(

> 
> diff --git a/include/linux/cxl-event.h b/include/linux/cxl-event.h
> index 2b137aead750..975925029f6d 100644
> --- a/include/linux/cxl-event.h
> +++ b/include/linux/cxl-event.h
> @@ -130,12 +130,12 @@ struct cxl_cper_event_rec {
>                         u16 segment_num;
>                         u16 slot_num; /* bits 2:0 reserved */
>                         u8 reserved;
> -               } device_id __packed;
> +               } __packed device_id;
>                 struct cper_cxl_event_sn {
>                         u32 lower_dw;
>                         u32 upper_dw;
> -               } dev_serial_num __packed;
> -       } hdr __packed;
> +               } __packed dev_serial_num;
> +       } __packed hdr;
>  
>         union cxl_event event;
>  } __packed;
> 

Yes thanks,
Ira