Message-ID: <878da778-e183-6ef5-61ce-3a3d059f1a1e@redhat.com>
Date:   Mon, 18 Sep 2023 16:07:53 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Mark Pearson <mpearson-lenovo@...ebb.ca>
Cc:     markgross@...nel.org, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] platform/x86: think-lmi: Add bulk save feature

Hi,

On 9/18/23 15:57, Andy Shevchenko wrote:
> On Wed, Sep 06, 2023 at 08:13:14AM -0400, Mark Pearson wrote:
>> On Lenovo platforms there is a limitation in the number of times an
>> attribute can be saved. This is an architectural limitation and it limits
>> the number of attributes that can be modified to 48.
>> A solution for this is instead of the attribute being saved after every
>> modification allow a user to bulk set the attributes and then trigger a
>> final save. This allows unlimited attributes.
>>
>> This patch introduces a save_settings attribute that can be configured to
>> either single or bulk mode by the user.
>> Single mode is the default but customers who want to avoid the 48
>> attribute limit can enable bulk mode.
>>
>> Displaying the save_settings attribute will display the enabled mode.
>>
>> When in bulk mode writing 'save' to the save_settings attribute will
>> trigger a save. Once this has been done a reboot is required before more
>> attributes can be modified.
> 
> ...
> 
>> +Date:		August 2023
>> +KernelVersion:	6.5
> 
> This is obviously incorrect (outdated) information.

Mark can you please submit a follow up patch fixing this.

> 
> ...
> 
>> +static const char * const save_mode_strings[] = {
>> +	[TLMI_SAVE_SINGLE] = "single",
>> +	[TLMI_SAVE_BULK] = "bulk",
>> +	[TLMI_SAVE_SAVE] = "save"
> 
> Missing comma.

Fixing this retro-actively is not really useful, if we
ever need an extra entry we can deal with the churn then.

> 
>> +};
> 
> ...
> 
>> +static ssize_t save_settings_show(struct kobject *kobj, struct kobj_attribute *attr,
>> +				  char *buf)
>> +{
>> +	/* Check that setting is valid */
>> +	if (WARN_ON((tlmi_priv.save_mode < TLMI_SAVE_SINGLE) ||
>> +		    (tlmi_priv.save_mode > TLMI_SAVE_BULK)))
>> +		return -EIO;
>> +	return sprintf(buf, "%s\n", save_mode_strings[tlmi_priv.save_mode]);
> 
> According to the documentation it must be sysfs_emit() if I'm not missing
> anything here.

Yes switching to sysfs_emit() here in the followup patch would be good.

> 
>> +}
> 
> ...
> 
>> +static ssize_t save_settings_store(struct kobject *kobj, struct kobj_attribute *attr,
>> +				   const char *buf, size_t count)
>> +{
>> +	char *auth_str = NULL;
>> +	int ret = 0;
>> +	int cmd;
>> +
>> +	cmd = sysfs_match_string(save_mode_strings, buf);
>> +
>> +	/* Use lock in case multiple WMI operations needed */
>> +	mutex_lock(&tlmi_mutex);
>> +
>> +	switch (cmd) {
>> +	case TLMI_SAVE_SINGLE:
>> +	case TLMI_SAVE_BULK:
>> +		tlmi_priv.save_mode = cmd;
>> +		goto out;
>> +	case TLMI_SAVE_SAVE:
>> +		/* Check if supported*/
>> +		if ((!tlmi_priv.can_set_bios_settings) ||
>> +		    (tlmi_priv.save_mode == TLMI_SAVE_SINGLE)) {
>> +			ret = -EOPNOTSUPP;
>> +			goto out;
>> +		}
>> +		/* Check there is actually something to save */
>> +		if (!tlmi_priv.save_required) {
>> +			ret = -ENOENT;
>> +			goto out;
>> +		}
>> +		/* Check if certificate authentication is enabled and active */
>> +		if (tlmi_priv.certificate_support && tlmi_priv.pwd_admin->cert_installed) {
>> +			if (!tlmi_priv.pwd_admin->signature ||
>> +			    !tlmi_priv.pwd_admin->save_signature) {
>> +				ret = -EINVAL;
>> +				goto out;
>> +			}
>> +			ret = tlmi_simple_call(LENOVO_SAVE_BIOS_SETTING_CERT_GUID,
>> +					       tlmi_priv.pwd_admin->save_signature);
>> +			if (ret)
>> +				goto out;
>> +		} else if (tlmi_priv.opcode_support) {
>> +			if (tlmi_priv.pwd_admin->valid && tlmi_priv.pwd_admin->password[0]) {
>> +				ret = tlmi_opcode_setting("WmiOpcodePasswordAdmin",
>> +							  tlmi_priv.pwd_admin->password);
>> +				if (ret)
>> +					goto out;
>> +			}
>> +			ret = tlmi_save_bios_settings("");
>> +		} else { /* old non-opcode based authentication method (deprecated) */
>> +			if (tlmi_priv.pwd_admin->valid && tlmi_priv.pwd_admin->password[0]) {
>> +				auth_str = kasprintf(GFP_KERNEL, "%s,%s,%s;",
>> +						     tlmi_priv.pwd_admin->password,
>> +						     encoding_options[tlmi_priv.pwd_admin->encoding],
>> +						     tlmi_priv.pwd_admin->kbdlang);
>> +				if (!auth_str) {
>> +					ret = -ENOMEM;
>> +					goto out;
>> +				}
>> +			}
>> +
>> +			if (auth_str)
>> +				ret = tlmi_save_bios_settings(auth_str);
>> +			else
>> +				ret = tlmi_save_bios_settings("");
>> +		}
>> +		tlmi_priv.save_required = false;
>> +		tlmi_priv.reboot_required = true;
>> +
>> +		if (!ret && !tlmi_priv.pending_changes) {
>> +			tlmi_priv.pending_changes = true;
>> +			/* let userland know it may need to check reboot pending again */
>> +			kobject_uevent(&tlmi_priv.class_dev->kobj, KOBJ_CHANGE);
>> +		}
>> +		break;
> 
>> +	default:
>> +		ret = -EINVAL;
>> +	}
> 
> Missing break; and actually no need to do this part under the lock, besides
> that it shadows an error code, that said this should be
> 
> 	cmd = sysfs_match_string(...);
> 	if (cmd < 0)
> 		return cmd;
> 
> 
>> +out:
>> +	mutex_unlock(&tlmi_mutex);
>> +	kfree(auth_str);
>> +	return ret ?: count;
> 
> You can switch the driver to use cleanup.h at some point.
> 
>> +}
> 
> ...
> 
>> +/* There are a limit on the number of WMI operations you can do if you use
>> + * the default implementation of saving on every set. This is due to a
>> + * limitation in EFI variable space used.
>> + * Have a 'bulk save' mode where you can manually trigger the save, and can
>> + * therefore set unlimited variables - for users that need it.
>> + */
> 
> /*
>  * This is wrong multi-line comment style. This one
>  * is used solely in net subsystem.
>  */
> 

Good catch, Mark can you fix this one too please ?

Also I thought that checkpatch.pl used to catch this ?

Regards,

hans

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