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Date:   Thu, 6 Feb 2020 13:16:30 +0100
From:   Jean Delvare <jdelvare@suse.de>
To:     Erwan Velu <erwanaliasr1@gmail.com>
Cc:     Erwan Velu <e.velu@criteo.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Michal Marek <michal.lkml@markovi.net>,
        Mattias Jacobsson <2pi@mok.nu>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "David S. Miller" <davem@davemloft.net>,
        Changbin Du <changbin.du@intel.com>,
        "Robert P. J. Day" <rpjday@crashcourse.ca>,
        Sumit Garg <sumit.garg@linaro.org>,
        linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org
Subject: Re: [PATCH 1/2] firmware/dmi: Report DMI Bios release
Message-ID: <20200206131630.4b18472e@endymion>
In-Reply-To: <20191127150729.860625-1-e.velu@criteo.com>
References: <20190918094323.17515-1-e.velu@criteo.com>
        <20191127150729.860625-1-e.velu@criteo.com>
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Hi Erwan,

Once again, sorry for the late answer.

On Wed, 27 Nov 2019 16:07:25 +0100, Erwan Velu wrote:
> Some vendors like HPe or Dell, encode the release version of their BIOS
> in the "System BIOS {Major|Minor} Release" fields of Type 0.
> 
> This information is used to know which bios release actually runs.
> It could be used for some quirks, debugging sessions or inventory tasks.
> 
> A typical output for a Dell system running the 65.27 bios is :
> 
> 	[root@t1700 ~]# cat /sys/devices/virtual/dmi/id/bios_release
> 	65.27
> 	[root@t1700 ~]#
> 
> This commit add  dmi_save_release() function have the logic to
> check if the field is valid. If so, it reports the actual value.
> 
> Signed-off-by: Erwan Velu <e.velu@criteo.com>
> ---
>  drivers/firmware/dmi-id.c       |  3 +++
>  drivers/firmware/dmi_scan.c     | 29 +++++++++++++++++++++++++++++
>  include/linux/mod_devicetable.h |  1 +
>  scripts/mod/file2alias.c        |  1 +
>  4 files changed, 34 insertions(+)
> 
> diff --git a/drivers/firmware/dmi-id.c b/drivers/firmware/dmi-id.c
> index ff39f64f2aae..a2aac65ff771 100644
> --- a/drivers/firmware/dmi-id.c
> +++ b/drivers/firmware/dmi-id.c
> @@ -42,6 +42,7 @@ DEFINE_DMI_ATTR_WITH_SHOW(bios_vendor,		0444, DMI_BIOS_VENDOR);
>  DEFINE_DMI_ATTR_WITH_SHOW(bios_version,		0444, DMI_BIOS_VERSION);
>  DEFINE_DMI_ATTR_WITH_SHOW(bios_date,		0444, DMI_BIOS_DATE);
>  DEFINE_DMI_ATTR_WITH_SHOW(sys_vendor,		0444, DMI_SYS_VENDOR);
> +DEFINE_DMI_ATTR_WITH_SHOW(bios_release,         0444, DMI_BIOS_RELEASE);
>  DEFINE_DMI_ATTR_WITH_SHOW(product_name,		0444, DMI_PRODUCT_NAME);
>  DEFINE_DMI_ATTR_WITH_SHOW(product_version,	0444, DMI_PRODUCT_VERSION);
>  DEFINE_DMI_ATTR_WITH_SHOW(product_serial,	0400, DMI_PRODUCT_SERIAL);
> @@ -78,6 +79,7 @@ static ssize_t get_modalias(char *buffer, size_t buffer_size)
>  		{ "bvn", DMI_BIOS_VENDOR },
>  		{ "bvr", DMI_BIOS_VERSION },
>  		{ "bd",  DMI_BIOS_DATE },
> +		{ "br",  DMI_BIOS_RELEASE },
>  		{ "svn", DMI_SYS_VENDOR },
>  		{ "pn",  DMI_PRODUCT_NAME },
>  		{ "pvr", DMI_PRODUCT_VERSION },
> @@ -187,6 +189,7 @@ static void __init dmi_id_init_attr_table(void)
>  	ADD_DMI_ATTR(bios_vendor,       DMI_BIOS_VENDOR);
>  	ADD_DMI_ATTR(bios_version,      DMI_BIOS_VERSION);
>  	ADD_DMI_ATTR(bios_date,         DMI_BIOS_DATE);
> +	ADD_DMI_ATTR(bios_release,      DMI_BIOS_RELEASE);
>  	ADD_DMI_ATTR(sys_vendor,        DMI_SYS_VENDOR);
>  	ADD_DMI_ATTR(product_name,      DMI_PRODUCT_NAME);
>  	ADD_DMI_ATTR(product_version,   DMI_PRODUCT_VERSION);
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index 1e21fc3e9851..d010c915c1ab 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -181,6 +181,34 @@ static void __init dmi_save_ident(const struct dmi_header *dm, int slot,
>  	dmi_ident[slot] = p;
>  }
>  
> +static void __init dmi_save_release(const struct dmi_header *dm, int slot,
> +		int index)
> +{
> +	const u8 *minor, *major;
> +	char *s;
> +
> +	/* If the table doesn't have the field, let's return */
> +	if (dmi_ident[slot] || dm->length < index)
> +		return;
> +
> +	minor = (u8 *) dm + index;
> +	major = (u8 *) dm + index - 1;
> +
> +	/* As per the spec, if the system doesn't support this field,
> +	 * the value is FF
> +	 */
> +	if (major[0] == 0xFF && minor[0] == 0xFF)

When using a pointer to a single entity, the common practice is to use
*major rather than major[0].

> +		return;
> +
> +	s = dmi_alloc(4);

4 bytes (3 + 1) were enough when you encoded a single byte. Now that you
encode 2 bytes separates by a dot, you need 8 (3 + 1 + 3 + 1).

> +	if (!s)
> +		return;
> +
> +	sprintf(s, "%u.%u", major[0], minor[0]);

Here too, *major would be preferred.

> +
> +	dmi_ident[slot] = s;
> +}
> +
>  static void __init dmi_save_uuid(const struct dmi_header *dm, int slot,
>  		int index)
>  {
> @@ -438,6 +466,7 @@ static void __init dmi_decode(const struct dmi_header *dm, void *dummy)
>  		dmi_save_ident(dm, DMI_BIOS_VENDOR, 4);
>  		dmi_save_ident(dm, DMI_BIOS_VERSION, 5);
>  		dmi_save_ident(dm, DMI_BIOS_DATE, 8);
> +		dmi_save_release(dm, DMI_BIOS_RELEASE, 21);
>  		break;
>  	case 1:		/* System Information */
>  		dmi_save_ident(dm, DMI_SYS_VENDOR, 4);
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index 5714fd35a83c..618933d770e6 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -532,6 +532,7 @@ enum dmi_field {
>  	DMI_BIOS_VENDOR,
>  	DMI_BIOS_VERSION,
>  	DMI_BIOS_DATE,
> +	DMI_BIOS_RELEASE,
>  	DMI_SYS_VENDOR,
>  	DMI_PRODUCT_NAME,
>  	DMI_PRODUCT_VERSION,
> diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> index c91eba751804..cc48930cc02a 100644
> --- a/scripts/mod/file2alias.c
> +++ b/scripts/mod/file2alias.c
> @@ -936,6 +936,7 @@ static const struct dmifield {
>  	{ "bvn", DMI_BIOS_VENDOR },
>  	{ "bvr", DMI_BIOS_VERSION },
>  	{ "bd",  DMI_BIOS_DATE },
> +	{ "br",  DMI_BIOS_RELEASE },
>  	{ "svn", DMI_SYS_VENDOR },
>  	{ "pn",  DMI_PRODUCT_NAME },
>  	{ "pvr", DMI_PRODUCT_VERSION },


-- 
Jean Delvare
SUSE L3 Support