Add SPI 25xx EEPROM support. (#8780)

drivers/eeprom/eeprom_spi.h

@@ -0,0 +1,80 @@
+/* Copyright 2020 Nick Brassel (tzarc)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+/*
+    The slave select pin of the EEPROM.
+    This needs to be a normal GPIO pin_t value, such as A7.
+*/
+#ifndef EXTERNAL_EEPROM_SPI_SLAVE_SELECT_PIN
+#    error "No chip select pin defined -- missing EXTERNAL_EEPROM_SPI_SLAVE_SELECT_PIN"
+#endif
+
+/*
+    The clock divisor for SPI to ensure that the MCU is within the
+    specifications of the EEPROM chip. Generally this will be PCLK divided by
+    the intended divisor -- check your clock settings and the datasheet of
+    your EEPROM.
+*/
+#ifndef EXTERNAL_EEPROM_SPI_CLOCK_DIVISOR
+#    ifdef __AVR__
+#        define EXTERNAL_EEPROM_SPI_CLOCK_DIVISOR 8
+#    else
+#        define EXTERNAL_EEPROM_SPI_CLOCK_DIVISOR 64
+#    endif
+#endif
+
+/*
+    The SPI mode to communicate with the EEPROM.
+*/
+#ifndef EXTERNAL_EEPROM_SPI_MODE
+#    define EXTERNAL_EEPROM_SPI_MODE 0
+#endif
+
+/*
+    Whether or not the SPI communication between the MCU and EEPROM should be
+    LSB-first.
+*/
+#ifndef EXTERNAL_EEPROM_SPI_LSBFIRST
+#    define EXTERNAL_EEPROM_SPI_LSBFIRST false
+#endif
+
+/*
+    The total size of the EEPROM, in bytes. The EEPROM datasheet will usually
+    specify this value in kbits, and will require conversion to bytes.
+*/
+#ifndef EXTERNAL_EEPROM_BYTE_COUNT
+#    define EXTERNAL_EEPROM_BYTE_COUNT 8192
+#endif
+
+/*
+    The page size in bytes of the EEPROM, as specified in the datasheet.
+*/
+#ifndef EXTERNAL_EEPROM_PAGE_SIZE
+#    define EXTERNAL_EEPROM_PAGE_SIZE 32
+#endif
+
+/*
+    The address size in bytes of the EEPROM. For EEPROMs with <=256 bytes, this
+    will likely be 1. For EEPROMs >256 and <=65536, this will be 2. For EEPROMs
+    >65536, this will likely need to be 4.
+
+    As expected, consult the datasheet for specifics of your EEPROM.
+*/
+#ifndef EXTERNAL_EEPROM_ADDRESS_SIZE
+#    define EXTERNAL_EEPROM_ADDRESS_SIZE 2
+#endif