Clarify that cache is flushed, but that function is intended for low-level metadata access during startup (#322)
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@ -83,14 +83,24 @@ void flash_get_unique_id(uint8_t *id_out);
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/*! \brief Execute bidirectional flash command
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/*! \brief Execute bidirectional flash command
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* \ingroup hardware_flash
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* \ingroup hardware_flash
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*
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*
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* Execute a bidirectional command to the flash. Bytes are simultaneously
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* Low-level function to execute a serial command on a flash device attached
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* transmitted and received. Therefore, both buffers must be the same length,
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* to the QSPI interface. Bytes are simultaneously transmitted and received
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* from txbuf and to rxbuf. Therefore, both buffers must be the same length,
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* count, which is the length of the overall transaction. This is useful for
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* count, which is the length of the overall transaction. This is useful for
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* reading metadata from the flash chip. Do *NOT* use it to mutate the data
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* reading metadata from the flash chip, such as device ID or SFDP
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* stored on the flash because it will not flush the cache.
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* parameters.
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*
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* The XIP cache is flushed following each command, in case flash state
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* has been modified. Like other hardware_flash functions, the flash is not
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* accessible for execute-in-place transfers whilst the command is in
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* progress, so entering a flash-resident interrupt handler or executing flash
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* code on the second core concurrently will be fatal. To avoid these pitfalls
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* it is recommended that this function only be used to extract flash metadata
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* during startup, before the main application begins to run: see the
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* implementation of pico_get_unique_id() for an example of this.
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*
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*
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* \param txbuf Pointer to a byte buffer which will be transmitted to the flash
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* \param txbuf Pointer to a byte buffer which will be transmitted to the flash
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* \param rxbuf Pointer to a byte buffer where data received from the flash will be written
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* \param rxbuf Pointer to a byte buffer where data received from the flash will be written. txbuf and rxbuf may be the same buffer.
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* \param count Length in bytes of txbuf and of rxbuf
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* \param count Length in bytes of txbuf and of rxbuf
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*/
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*/
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void flash_do_cmd(const uint8_t *txbuf, uint8_t *rxbuf, size_t count);
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void flash_do_cmd(const uint8_t *txbuf, uint8_t *rxbuf, size_t count);
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