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You are referring to the wrong document (PXE 2.1 spec for 16-bit
UNDIs/legacy BIOS).<br>
Appendix E of UEFI specification defines UNDI functions, behaviors
and supported opcodes in UEFI.<br>
<br>
Thanks,<br>
Maciej<br>
<br>
<div class="moz-cite-prefix">On 26-Nov-20 17:20, Sivaraman Nainar
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:B4DE137BDB63634BAC03BD9DE765F19702B4B9D428@VENUS1.in.megatrends.com">
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<p class="MsoNormal"><span style="color:#1F497D">Hello Maciej:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="color:#1F497D">As per the
PXE Specification:
<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="color:#1F497D">The protocol
driver calls UNDI repeatedly with the FuncFlag equal to
PXENV_UNDI_ISR_IN_GET_NEXT to get all the buffers in a frame
and also all the received<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">frames in the
queue. On this call, UNDI must remember the previous buffer
given to the protoco,l remove it from the receive queue and
recycle it. In case of a multi-buffered frame, if the
previous<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">buffer is not
the last buffer in the frame it must return the next buffer
in the frame in the parameter block. Otherwise it must
return the first buffer in the next frame.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Assume the UNDI
Driver does not properly Store that TxAddress in the
GetStatus then the possibility of MNP Layer having issues
when it treats the recycling based on the GetStatus.<o:p></o:p></span></p>
<p class="MsoNormal">2. If a NIC has a pre-allocated region for
Tx buffers and cannot dynamically swap them out,
UNDI->Transmit() should copy the Tx buffer into appropriate
region. UNDI driver should also store that Tx buffer somewhere
within the driver, where it will be accessible by
UNDI->GetStatus() function.<br>
<br>
<span style="color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">When this point
2 fails the Recycle support done in the SW Layer shall also
fail.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Pleases correct
my understanding if any .
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">-Siva<o:p></o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b>From:</b> Rabeda, Maciej
[<a class="moz-txt-link-freetext" href="mailto:maciej.rabeda@linux.intel.com">mailto:maciej.rabeda@linux.intel.com</a>]
<br>
<b>Sent:</b> Thursday, November 26, 2020 9:10 PM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:devel@edk2.groups.io">devel@edk2.groups.io</a>; Sivaraman Nainar<br>
<b>Subject:</b> Re: [edk2-devel] reg: PCD To Control MNP
Buffer Recycle Support<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi Nainar,<br>
<br>
What do you mean by "controllers do not support recycling of
Tx buffers"?<br>
MNP provides a transmit buffer to SNP (and with EDK2's SNP
also to UNDI) and at this point it is considered owned by
SNP/UNDI.<br>
After UNDI/SNP successfully transmits the packet, it is
expected to give it back via UNDI->GetStatus().<br>
<br>
Adding network controller (NIC) and UNDI into the picture.<br>
<br>
1. UNDI->Transmit() gets a single Tx buffer to put on the
wire.<br>
2. If a NIC has a pre-allocated region for Tx buffers and
cannot dynamically swap them out, UNDI->Transmit() should
copy the Tx buffer into appropriate region. UNDI driver should
also store that Tx buffer somewhere within the driver, where
it will be accessible by UNDI->GetStatus() function.<br>
3. After successful transmit of Tx buffer, on next
UNDI->GetStatus() with PXE_OPFLAGS_GET_TRANSMITTED_BUFFERS
OpFlag, driver should put that Tx buffer address in
PXE_CDB.DBAddr provided to UNDI->GetStatus() as a
parameter.<br>
<br>
Summing the above - Tx buffer recycling is purely a SW
feature. I do not understand your request nor find it valid.<br>
<br>
Thanks,<br>
Maciej<span style="font-size:12.0pt"><o:p></o:p></span></p>
<div>
<p class="MsoNormal">On 24-Nov-20 15:30, Sivaraman Nainar
wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Hello all:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">MNPDxe supported with the Recycle buffer
support from the below git commit,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><a
href="https://github.com/tianocore/edk2/commit/0507449955c5c629cec196b62986afbb91203ed9#diff-fb5b97ad38efea22f5ddd745f6e43ebdb509dc4a5aef81997ba53af5f918a47b"
moz-do-not-send="true">https://github.com/tianocore/edk2/commit/0507449955c5c629cec196b62986afbb91203ed9#diff-fb5b97ad38efea22f5ddd745f6e43ebdb509dc4a5aef81997ba53af5f918a47b</a><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">But many network controllers does not
support the Recycling Tx Buffers which will cause the PXE
Download failure or HTTP Boot failure.
<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Can this feature can be controlled by a
Dynamic PCD so that the same code can work for controller
which does not support Tx Buffer Recycling.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Thanks<o:p></o:p></p>
<p class="MsoNormal">Siva<o:p></o:p></p>
<div>
</div>
</blockquote>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Times New
Roman","serif""><o:p> </o:p></span></p>
</div>
</blockquote>
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