fix(msc): set min buffer cap to usb packet size

Author: mikesmitty

src/machine/usb/msc/disk.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"machine"
+	"machine/usb"
 	"time"
 )
 
@@ -17,8 +18,8 @@ func (m *msc) RegisterBlockDevice(dev machine.BlockDevice) {
 	m.dev = dev
 
 	if cap(m.blockCache) != int(dev.WriteBlockSize()) {
-		m.blockCache = make([]byte, dev.WriteBlockSize())
-		m.buf = make([]byte, dev.WriteBlockSize())
+		m.blockCache = make([]byte, max(usb.EndpointPacketSize, dev.WriteBlockSize()))
+		m.buf = make([]byte, max(usb.EndpointPacketSize, dev.WriteBlockSize()))
 	}
 
 	m.blockSizeRaw = uint32(m.dev.WriteBlockSize())

src/machine/usb/msc/msc.go

@@ -72,9 +72,9 @@ func newMSC(dev machine.BlockDevice) *msc {
 	maxPacketSize := descriptor.EndpointMSCIN.GetMaxPacketSize()
 	m := &msc{
 		// Some platforms require reads/writes to be aligned to the full underlying hardware block
-		blockCache:    make([]byte, dev.WriteBlockSize()),
+		blockCache:    make([]byte, max(usb.EndpointPacketSize, dev.WriteBlockSize())),
 		blockSizeUSB:  512,
-		buf:           make([]byte, dev.WriteBlockSize()),
+		buf:           make([]byte, max(usb.EndpointPacketSize, dev.WriteBlockSize())),
 		cswBuf:        make([]byte, csw.MsgLen),
 		cbw:           &CBW{Data: make([]byte, 31)},
 		maxPacketSize: uint32(maxPacketSize),