SPI usage questions

[Bernd Walter <ti...@cicely7.cicely.de>]

While looking into the mcp2515 driver I noticed something unexpected.

In mcp2515_instantiate() it does the follofing:
  SPI_SETFREQUENCY(config->spi, CONFIG_MCP2515_SPI_SCK_FREQUENCY);
  SPI_SETMODE(config->spi, MCP2515_SPI_MODE);
  SPI_SETBITS(config->spi, 8);
  SPI_HWFEATURES(config->spi, 0);

In mcp2515_read_2regs() and all the other transfer functions it does the
following:
  SPI_LOCK(priv->config->spi, true);
  SPI_SELECT(priv->config->spi, SPIDEV_CANBUS(0), true);
  SPI_EXCHANGE(priv->config->spi, priv->spi_txbuf, priv->spi_rxbuf, 4);
  SPI_SELECT(priv->config->spi, SPIDEV_CANBUS(0), false);
  SPI_LOCK(priv->config->spi, false);

What puzzles me is that all he mode settings are done without locking
the SPI and only once during the init phase.
I would have expected it to be done in each and every transfer within
the LOCK region.
When I look into the e.g. RP2040 code then the config->spi doesn't look
to be unique for the single mcp2515 instance.

-- 
B.Walter <be...@bwct.de> https://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.