linux-kernel - Re: [PATCH 0/6] mailbox: pcc: Refactor and improve initialisation and interrupt handling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ed1963c8-207d-4003-bff8-800b76c30b29@amperemail.onmicrosoft.com>
Date: Thu, 5 Feb 2026 02:31:54 -0500
From: Adam Young <admiyo@...eremail.onmicrosoft.com>
To: Sudeep Holla <sudeep.holla@...nel.org>
Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
 Jassi Brar <jassisinghbrar@...il.com>,
 Adam Young <admiyo@...amperecomputing.com>,
 Robbie King <robbiek@...ghtlabs.com>, Huisong Li <lihuisong@...wei.com>,
 Cristian Marussi <cristian.marussi@....com>
Subject: Re: [PATCH 0/6] mailbox: pcc: Refactor and improve initialisation and
 interrupt handling


On 2/4/26 16:40, Adam Young wrote:
> I was just looking at it.  I think reposting might cause too much 
> churn, when the  crux of the matter is what to do with these three 
> functions I added:
>
> extern struct pcc_mbox_chan *
> pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id);
> extern void pcc_mbox_free_channel(struct pcc_mbox_chan *chan);
> extern
> int pcc_mbox_write_to_buffer(struct pcc_mbox_chan *pchan, int len, 
> void *data);
> extern
> int pcc_mbox_query_bytes_available(struct pcc_mbox_chan *pchan);
> extern
> int pcc_mbox_read_from_buffer(struct pcc_mbox_chan *pchan, int len,
>                               void *data);
>
> In my last patch I added them as EXPORT_SYMBOL_GPL.  You mentioned you 
> wanted them as inline.
>
> We can do that, but it does mean further exposing the ACPI header 
> file.  THe simplest is  pcc_mbox_query_bytes_available which I have 
> posted below.  As you can see, it needs the struct 
> acpi_pcct_ext_pcc_shared_memory  which comes from 
> include/acpi/actbl2.h.  If you are OK with adding that to 
> include/acpi/pcc.h  We can inline the functions in there.

Actually, I just looked, and the more significant issue is that they 
need access to struct pcc_chan_info, which is inside of mailbox/pcc.c, 
and thus not available to client code.  While we could move this 
structure to the header, I think the better approach is what I 
originally posted, with the 3 additional functions exported as symbols.

I can resubmit it this way, if you agree.

>
> These three functions are requied as a result of the direct access to 
> the shared memory buffer.
>
>
> int pcc_mbox_query_bytes_available(struct pcc_mbox_chan *pchan)
> {
>         struct acpi_pcct_ext_pcc_shared_memory pcc_header;
>         struct pcc_chan_info *pinfo = pchan->mchan->con_priv;
>         int data_len;
>         u64 val;
>
>         pcc_chan_reg_read(&pinfo->cmd_complete, &val);
>         if (val) {
>                 pr_info("%s Buffer not enabled for reading", __func__);
>                 return -1;
>         }
>         memcpy_fromio(&pcc_header, pchan->shmem,
>                       sizeof(pcc_header));
>         data_len = pcc_header.length - sizeof(u32) + sizeof(pcc_header);
>         return data_len;
> }
>
>
>
>
> On 1/27/26 04:29, Sudeep Holla wrote:
>> On Mon, Jan 26, 2026 at 12:07:26PM -0500, Adam Young wrote:
>>>
>>> On 1/12/26 11:55, Sudeep Holla wrote:
>>>> On Thu, Nov 27, 2025 at 02:40:56PM +0000, Sudeep Holla wrote:
>>>>> Hi Jassi,
>>>>>
>>>>> On Thu, Oct 16, 2025 at 08:08:14PM +0100, Sudeep Holla wrote:
>>>>>> This series refines and stabilizes the PCC mailbox driver to improve
>>>>>> initialisation order, interrupt handling, and completion signaling.
>>>>>>
>>>>> Are you happy to pull these patches directly from the list or do you
>>>>> prefer me to send you pull request or do you want me to direct 
>>>>> this via
>>>>> ACPI/Rafael's tree. Please advice.
>>>>>
>>>> Hi Jassi,
>>>>
>>>> Sorry for the nag. I did see these patches in -next as well as your
>>>> v6.19 merge window pull request which didn't make it to Linus tree.
>>>> However I don't see it -next any longer. Please advice if you want
>>>> anything from my side so that this can be merged for v6.20/v7.0
>>>>
>>> I thought you had an approach you wanted to implement for the 
>>> functions that
>>> provided access to the Mailbox internals: you wanted to do them 
>>> inline but
>>> hadn't gotten to them yet.  Is that still the case?  I will resubmit 
>>> mine as
>>> is with -next if that is acceptable.
>>>
>> Honestly, it has been a while and I have lost the context. Please 
>> post what
>> you have or thinking of on top of linux-next or jassi's -next and we 
>> can start
>> the discussion fresh.
>>