STM32H legacy driver fix: request usable RX size in legacy zero-copy#1328
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…path The STM32H legacy zero-copy RX path still requested ETH_RX_BUF_SIZE for replacement RX buffers even though BufferAllocation_1 now limits allocations to the interface-reported usable size. For this driver the usable size is ETH_RX_BUF_SIZE - ipBUFFER_PADDING. Requesting the full hardware buffer size caused every replacement allocation to fail, left pxReceivedBuffer as NULL, and dropped all received frames before they reached the IP task. Request ETH_RX_BUF_SIZE - ipBUFFER_PADDING in the RX fast path so the receive path matches the enforced allocation limit.
htibosch
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Apr 4, 2026
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Thank you @liteStefanoUgolini for this PR. I approve it.
| uxLength = ETH_RX_BUF_SIZE; | ||
| /* Request the usable Ethernet payload area, excluding the descriptor | ||
| * metadata stored in front of pucEthernetBuffer. */ | ||
| uxLength = ETH_RX_BUF_SIZE - ipBUFFER_PADDING; |
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That sounds like a good change, thank you.
The sizeof of the RX buffer is usually set at :
#define ETH_RX_BUF_SIZE 1536U
because it has a great alignment ( 0x600 ).
@AniruddhaKanhere @kstribrnAmzn Can you please check this PR?
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Description
The STM32H legacy zero-copy RX path still requested ETH_RX_BUF_SIZE for replacement RX buffers even though BufferAllocation_1 now limits allocations to the interface-reported usable size.
For this driver the usable size is ETH_RX_BUF_SIZE - ipBUFFER_PADDING. Requesting the full hardware buffer size caused every replacement allocation to fail, left pxReceivedBuffer as NULL, and dropped all received frames before they reached the IP task.
Request ETH_RX_BUF_SIZE - ipBUFFER_PADDING in the RX fast path so the receive path matches the enforced allocation limit.
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