drv/block_device_w25qxx_stm32: move size out of linker script

This driver is for external flash, so it doesn't make sense to put
some of it's config in the linker script (which only deals with
internal flash). This moves the config from the linker script to the
platform.c file where the rest of the config already is.

Also changed a couple while loops to for loops to make the code more
idiomatic while we are touching this.

bricks/debug/debug.ld

@@ -10,4 +10,3 @@ MEMORY
 }
 
 _stack_size = 8K;
-_pbdrv_block_device_storage_size = 64K;

bricks/essentialhub/essential_hub.ld

@@ -19,10 +19,3 @@ MEMORY
 
 "FW_INFO_OFFSET" = 0x200;
 _stack_size = 16K;
-
-/**
- * External flash storage size for 1 application program. The full user program
- * is loaded into RAM to run it, so the storage must not be bigger than RAM.
- * We also need to allow some RAM for bss and heap, so set storage a bit lower.
- */
-_pbdrv_block_device_storage_size = 256K;

bricks/primehub/prime_hub.ld

@@ -18,10 +18,3 @@ MEMORY
 }
 
 _stack_size = 16K;
-
-/**
- * External flash storage size for 1 application program. The full user program
- * is loaded into RAM to run it, so the storage must not be bigger than RAM.
- * We also need to allow some RAM for bss and heap, so set storage a bit lower.
- */
-_pbdrv_block_device_storage_size = 256K;

lib/pbio/drv/block_device/block_device_w25qxx_stm32.c

@@ -373,12 +373,11 @@ PT_THREAD(pbdrv_block_device_read(struct pt *pt, uint32_t offset, uint8_t *buffe
     bdev.process = PROCESS_CURRENT();
 
     // Split up reads to maximum chunk size.
-    size_done = 0;
-    while (size_done < size) {
+    for (size_done = 0; size_done < size; size_done += size_now) {
         size_now = pbio_math_min(size - size_done, FLASH_SIZE_READ);
 
         // Set address for this read request and send it.
-        set_address_be(&cmd_request_read.buffer[1], bdev.pdata->first_safe_write_address + offset + size_done);
+        set_address_be(&cmd_request_read.buffer[1], bdev.pdata->start_address + offset + size_done);
         PT_SPAWN(pt, &child, spi_command_thread(&child, &cmd_request_read, err));
         if (*err != PBIO_SUCCESS) {
             goto out;
@@ -391,8 +390,6 @@ PT_THREAD(pbdrv_block_device_read(struct pt *pt, uint32_t offset, uint8_t *buffe
         if (*err != PBIO_SUCCESS) {
             goto out;
         }
-
-        size_done += size_now;
     }
 
 out:
@@ -486,22 +483,20 @@ PT_THREAD(pbdrv_block_device_store(struct pt *pt, uint8_t *buffer, uint32_t size
     for (offset = 0; offset < size; offset += FLASH_SIZE_ERASE) {
         // Writing size 0 means erase.
         PT_SPAWN(pt, &child, flash_erase_or_write(&child,
-            bdev.pdata->first_safe_write_address + offset, NULL, 0, err));
+            bdev.pdata->start_address + offset, NULL, 0, err));
         if (*err != PBIO_SUCCESS) {
             goto out;
         }
     }
 
     // Write page by page.
-    size_done = 0;
-    while (size_done < size) {
+    for (size_done = 0; size_done < size; size_done += size_now) {
         size_now = pbio_math_min(size - size_done, FLASH_SIZE_WRITE);
         PT_SPAWN(pt, &child, flash_erase_or_write(&child,
-            bdev.pdata->first_safe_write_address + size_done, buffer + size_done, size_now, err));
+            bdev.pdata->start_address + size_done, buffer + size_done, size_now, err));
         if (*err != PBIO_SUCCESS) {
             goto out;
         }
-        size_done += size_now;
     }
 
 out:
@@ -511,10 +506,7 @@ PT_THREAD(pbdrv_block_device_store(struct pt *pt, uint8_t *buffer, uint32_t size
 }
 
 uint32_t pbdrv_block_device_get_size(void) {
-    // Defined in linker script. To get the numeric value assigned there, we
-    // need to read the address and cast to uint32_t.
-    extern uint32_t _pbdrv_block_device_storage_size;
-    return (uint32_t)(&_pbdrv_block_device_storage_size);
+    return bdev.pdata->end_address - bdev.pdata->start_address;
 }
 
 PROCESS(pbdrv_block_device_w25qxx_stm32_init_process, "w25qxx");

lib/pbio/drv/block_device/block_device_w25qxx_stm32.h

@@ -46,7 +46,9 @@ typedef struct {
      * this chip address. This can be used to protect the first region of flash
      * if it is used to store things like bootloader information.
      */
-    uint32_t first_safe_write_address;
+    uint32_t start_address;
+    /** Ending address (exclusive) complementary to the start_address. */
+    uint32_t end_address;
 } pbdrv_block_device_w25qxx_stm32_platform_data_t;
 
 /**

lib/pbio/platform/essential_hub/platform.c

@@ -630,7 +630,12 @@ const pbdrv_block_device_w25qxx_stm32_platform_data_t pbdrv_block_device_w25qxx_
         .bank = GPIOB,
         .pin = 12,
     },
-    .first_safe_write_address = 512 * 1024,
+    // Carve out 256K from the reserved 1M area at the start of the flash.
+    // This avoids touching the file system, the area read by the LEGO
+    // bootloader and the area used by upstream MicroPython. Currently, this
+    // just needs to be big enough to back up the user program on shutdown.
+    .start_address = 512 * 1024,
+    .end_address = 768 * 1024,
 };
 
 // USB

lib/pbio/platform/prime_hub/platform.c

@@ -923,7 +923,12 @@ const pbdrv_block_device_w25qxx_stm32_platform_data_t pbdrv_block_device_w25qxx_
         .bank = GPIOB,
         .pin = 12,
     },
-    .first_safe_write_address = 512 * 1024,
+    // Carve out 256K from the reserved 1M area at the start of the flash.
+    // This avoids touching the file system, the area read by the LEGO
+    // bootloader and the area used by upstream MicroPython. Currently, this
+    // just needs to be big enough to back up the user program on shutdown.
+    .start_address = 512 * 1024,
+    .end_address = 768 * 1024,
 };
 
 // USB