Re: [PATCH v3] mhi: host: Add standard elf image download functionality

On 12/18/2025 5:13 PM, Baochen Qiang wrote:
> 
> 
> On 12/18/2025 4:04 PM, Qiang Yu wrote:
>> On Thu, Dec 18, 2025 at 10:25:08AM +0530, Manivannan Sadhasivam wrote:
>>> On Tue, Dec 16, 2025 at 12:26:41AM -0800, Qiang Yu wrote:
>>>> On Mon, Dec 15, 2025 at 08:41:32PM +0200, Dmitry Baryshkov wrote:
>>>>> On Sun, Dec 14, 2025 at 11:09:58PM -0800, Qiang Yu wrote:
>>>>>> On Sat, Dec 13, 2025 at 11:21:11AM +0900, Manivannan Sadhasivam wrote:
>>>>>>> On Fri, Dec 12, 2025 at 09:24:06PM +0200, Dmitry Baryshkov wrote:
>>>>>>>> On Fri, Dec 12, 2025 at 10:07:01AM +0900, Manivannan Sadhasivam wrote:
>>>>>>>>> On Thu, Dec 11, 2025 at 03:57:54PM +0200, Dmitry Baryshkov wrote:
>>>>>>>>>> On Thu, Dec 11, 2025 at 01:37:12AM -0800, Qiang Yu wrote:
>>>>>>>>>>> On Wed, Dec 10, 2025 at 12:57:11AM +0200, Dmitry Baryshkov wrote:
>>>>>>>>>>>> On Sun, Dec 07, 2025 at 10:35:26PM -0800, Qiang Yu wrote:
>>>>>>>>>>>>> On Sat, Dec 06, 2025 at 01:25:34PM +0200, Dmitry Baryshkov wrote:
>>>>>>>>>>>>>> On Mon, Dec 01, 2025 at 06:33:15PM -0800, Qiang Yu wrote:
>>>>>>>>>>>>>>> From: Mayank Rana <[email protected]>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Currently, the FBC image is a non-standard ELF file that contains a single
>>>>>>>>>>>>>>> ELF header, followed by segments for SBL, and WLAN FW. However, TME-L
>>>>>>>>>>>>>>> (Trust Management Engine Lite) supported devices (eg. QCC2072) requires
>>>>>>>>>>>>>>> separate ELF headers for SBL and WLAN FW segments due to TME-L image
>>>>>>>>>>>>>>> authentication requirement.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Current image format contains two sections in a single binary:
>>>>>>>>>>>>>>> - First 512KB: ELF header + SBL segments
>>>>>>>>>>>>>>> - Remaining: WLAN FW segments
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> The TME-L supported image format contains two sections with two elf
>>>>>>>>>>>>>>> headers in a single binary:
>>>>>>>>>>>>>>> - First 512KB: First ELF header + SBL segments
>>>>>>>>>>>>>>> - Remaining: Second ELF header + WLAN FW segments
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Download behavior:
>>>>>>>>>>>>>>> - Legacy: 1. First 512KB via BHI (ELF header + SBL)
>>>>>>>>>>>>>>>           2. Full image via BHIe
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> - TME-L: 1. First 512KB via BHI (First ELF header + SBL)
>>>>>>>>>>>>>>>          2. Remaining via BHIe (Second ELF header + WLAN FW segments)
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Add standard_elf_image flag to mhi_controller_config to indicate TME-L
>>>>>>>>>>>>>>> supported image format. When set, MHI skips the first 512KB during WLAN FW
>>>>>>>>>>>>>>> download over BHIe as it is loaded in BHI phase.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> What is standard about it?
>>>>>>>>>>>>>
>>>>>>>>>>>>> The TME-L requires standard elf image format which includes single EFL
>>>>>>>>>>>>> header and WLAN FW segment.
>>>>>>>>>>>>>
>>>>>>>>>>>>> The "standard_elf_image" seems misleading. Since the new image format is
>>>>>>>>>>>>> required for TME-L image authentication, how about using 
>>>>>>>>>>>>> tme_supported_image?
>>>>>>>>>>>>
>>>>>>>>>>>> Just elf_image?
>>>>>>>>>>>
>>>>>>>>>>> Is it too generic for this specific use case. Current image format also
>>>>>>>>>>> contains elf header.
>>>>>>>>>>
>>>>>>>>>> upload_elf_image?
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Nope. What does 'upload' even mean here? The 'TIS and ELF' spec v1.2 clearly
>>>>>>>>> defines that an ELF executable can have only one ELF header. So I'd prefer
>>>>>>>>> 'standard_elf_image' to differentiate it from the non-spec-conformant ELF image
>>>>>>>>> used previously.
>>>>>>>>
>>>>>>>> What kind of ELF image was used previously? Could you please explain
>>>>>>>> what do 'First ELF header' vs 'Second ELF header' mean here?
>>>>>>>>
>>>>>>>
>>>>>>> I don't have the details of it, but Qiang should be able to explain. But AFAIC,
>>>>>>> that was a non-standard ELF image and the new one is going to be spec
>>>>>>> conformant.
>>>>>>>
>>>>>> Previous image format:
>>>>>> ELF header + SBL segments + WLAN FW segments
>>>>>>
>>>>>> The TME-L supported image format:
>>>>>> First ELF header + SBL segments + Second ELF header + WLAN FW segments
>>>>>
>>>>> What is the Second ELF header in this context? ELF files usually have
>>>>> only one header. Are we repeating the same ELF header or is some kind of
>>>>> an embedded ELF-in-ELF.
>>>>
>>>> The "Second ELF header" refers to a separate, complete ELF file embedded
>>>> within the FBC image, not a duplicate header. The TME-L supported format
>>>> contains:
>>>>
>>>> FBC Image Structure:
>>>> ┌─────────────────────────────────────┐
>>>> │  Complete ELF File #1 (SBL)        │
>>>> │  ┌─────────────────────────────┐   │
>>>> │  │ ELF Header                  │   │ ← First ELF header
>>>> │  │ Program Headers             │   │
>>>> │  │ SBL Segments                │   │
>>>> │  └─────────────────────────────┘   │
>>>> ├─────────────────────────────────────┤
>>>> │  Complete ELF File #2 (WLAN FW)    │
>>>> │  ┌─────────────────────────────┐   │
>>>> │  │ ELF Header                  │   │ ← Second ELF header
>>>> │  │ Program Headers             │   │
>>>> │  │ WLAN FW Segments            │   │
>>>> │  └─────────────────────────────┘   │
>>>> └─────────────────────────────────────┘
>>>>>
>>>>>>
>>>>>> As per 'TIS and ELF' spec v1.2 Mani mentioned, the previous image format
>>>>>
>>>>> pointer?
>>>>
>>>> The entire 'TIS and ELF' spec v1.2 document descibes the structure of the
>>>> ELF excutable file, I can not point out a specfic sentence or phase that
>>>> tell us the previous image format is standard. But at least there is an
>>>> example we can refer to: Figure A-4. Executable File Example. And I can
>>>> also use readelf cmd to parse the image.
>>>>
>>>>>
>>>>>> is also standard elf image. But it doesn't meet the requirement of TME-L
>>>>>> because we need separate elf header for SBL and WL FW for TME-L
>>>>>> authentication.
>>>>>>
>>>>>> So the commit message stating "Currently, the FBC image is a non-standard
>>>>>> ELF file that contains a single ELF header, followed by segments for SBL,
>>>>>> and WLAN FW" is not correct and standard_elf_image is not accurate.
>>>>>>
>>>>>> Can we avoid saying anything about standard in commit message? Flags eg.
>>>>>> separate_elf_header and tme_supported_image are more accurate.
>>>>>
>>>>> Please define, what is the supported image.
>>>>
>>>> The supported image refers to an image format that TME-L can authenticate.
>>>> Both SBL and WLAN FW should be in ELF format. After powering on, SBL (ELF
>>>> format, ELF header + SBL segment, first 512 KB) is loaded over BHI and
>>>> authenticated by TME-L. After entering SBL, WLAN FW (ELF format, skip
>>>> first 512KB of fbc image) is loaded over BHIe and also authenticated by
>>>> TME-L.
>>>>
>>>
>>> So what makes it different here is that you are now sending the two FWs
>>> separately as standalone ELF image to the device for authentication by TME-L,
>>> but those are combined in a single image file in the host. But what makes you to
>>> combine two images in the first place? Why can't they be separate ELF files?
>>>
>>> I think you can avoid the hassle if you could just have separate ELF images for
>>> SBL and WLAN FW and say that the TME-L just expects individual ELF image.
>>>
>> Yes, they are two separate images combined into a single file. I'm not
>> sure of the specific reasons for this design choice, so I can't comment
>> on it. The WLAN team provides a single file for both SBL and WLAN FW, and
>> I don't know whether they're willing to change.
>>
>> Baochen, do you have any comment on this?
> 
> Hmm, sorry, no idea :(

I mean I don't know the reason behind the design choice.

> 
>>
>> - Qiang Yu
>