Updating docs

part14-spi-ethernet/README.md

@@ -40,9 +40,16 @@ Let's start by looking at how we implement SPI communication.
 
 I'm not going to write a long paper on how SPI works and why we need it, because it's [very well documented elsewhere](https://learn.sparkfun.com/tutorials/serial-peripheral-interface-spi/). It's recommended background reading, but not essential if all you want to do is get something working.
 
-Look at _lib/spi.c_. It uses some of existing functions in _lib/io.c_ that you'll remember from earlier tutorials. Specifically, _spi_init()_ sets GPIO 7, 9, 10, and 11 to use the ALT0 function. Cross-referencing with the [BCM2711 ARM Peripherals document](https://datasheets.raspberrypi.com/bcm2711/bcm2711-peripherals.pdf), page 77, you'll see that this maps SPI0 to the GPIO header. GPIO 8 is mapped as an output pin, since we'll use this to signal to the ENC28J60 that we want to talk. In fact, the _spi_chip_select()_ function takes a true/false (boolean) parameter which either sets or clears this pin.
+Look at _lib/spi.c_. It uses some of existing functions in _lib/io.c_ that you'll remember from earlier tutorials. In fact, I've added two functions to the _include/io.h_ header file so we can call them from our SPI library:
 
-Looking at the SPI0 register map on page 134, we see this reflected in the _REGS_SPI0_ structure. This gives us handy access to the SPI0 peripheral's memory map.
+```c
+void gpio_setPinOutputBool(unsigned int pin_number, unsigned int onOrOff);
+void gpio_initOutputPinWithPullNone(unsigned int pin_number);
+```
+
+Specifically, _spi_init()_ sets GPIO 7, 9, 10, and 11 to use the ALT0 function. Cross-referencing with the [BCM2711 ARM Peripherals document](https://datasheets.raspberrypi.com/bcm2711/bcm2711-peripherals.pdf), page 77, you'll see that this maps SPI0 to the GPIO header. GPIO 8 is mapped as an output pin, since we'll use this to signal to the ENC28J60 that we want to talk. In fact, the _spi_chip_select()_ function takes a true/false (boolean) parameter which either sets or clears this pin.
+
+Looking at the SPI0 register map on page 134, we see this reflected in our _REGS_SPI0_ structure. This gives us handy access to the SPI0 peripheral's memory-mapped registers.
 
 Our _spi_send_recv()_ function then sets us up for some communcation:
 
@@ -54,4 +61,4 @@ Then, whilst there's either data to write or data to read (and we haven't writte
 
 Finally, to be absolutely sure, we clear the TA flag.
 
-I've then set up two convenient functions _spi_send()_ and _spi_recv()_ which exercise _spi_send_recv(), mainly to make future code more readable.
+I've then set up two convenient functions - _spi_send()_ and _spi_recv()_ - which exercise _spi_send_recv(), mainly to make future code more readable.

part14-spi-ethernet/include/spi.h

@@ -2,5 +2,4 @@ void spi_init();
 void spi_send_recv(unsigned char *sbuffer, unsigned char *rbuffer, unsigned int size);
 void spi_send(unsigned char *data, unsigned int size);
 void spi_recv(unsigned char *data, unsigned int size);
-void spi_send_no_selection(unsigned char command);
 void spi_chip_select(unsigned char chip_select);

part14-spi-ethernet/kernel/irq.c

@@ -1,27 +1,4 @@
 #include "kernel.h"
-#include "../include/fb.h"
-
-char *entry_error_messages[] = {
-   "SYNC_INVALID_EL1t",
-   "IRQ_INVALID_EL1t",		
-   "FIQ_INVALID_EL1t",		
-   "ERROR_INVALID_EL1T",		
-
-   "SYNC_INVALID_EL1h",		
-   "IRQ_INVALID_EL1h",		
-   "FIQ_INVALID_EL1h",		
-   "ERROR_INVALID_EL1h",		
-
-   "SYNC_INVALID_EL0_64",		
-   "IRQ_INVALID_EL0_64",		
-   "FIQ_INVALID_EL0_64",		
-   "ERROR_INVALID_EL0_64",	
-
-   "SYNC_INVALID_EL0_32",		
-   "IRQ_INVALID_EL0_32",		
-   "FIQ_INVALID_EL0_32",		
-   "ERROR_INVALID_EL0_32"	
-};
 
 void enable_interrupt_controller() {
     REGS_IRQ->irq0_enable_0 = SYS_TIMER_IRQ_1 | SYS_TIMER_IRQ_3;
@@ -31,14 +8,6 @@ void disable_interrupt_controller() {
     REGS_IRQ->irq0_enable_0 = 0;
 }
 
-void show_invalid_entry_message(int type, unsigned long esr, unsigned long address) {
-    debugstr(entry_error_messages[type]);
-    debugstr(" ESR: ");
-    debughex(esr);
-    debugstr("Addr: ");
-    debughex(address);
-}
-
 void handle_irq() {
     unsigned int irq = REGS_IRQ->irq0_pending_0;
 

part14-spi-ethernet/kernel/irqentry.S

@@ -67,7 +67,11 @@
 	mov	x0, #\type
 	mrs	x1, esr_el1
 	mrs	x2, elr_el1
-        bl      show_invalid_entry_message
+
+        // We could pass this to a function to print an error here
+        // e.g. bl show_invalid_entry_message
+        //
+        // For now we'll just hang
 
 	b	err_hang
 .endm