[HTC Desire 510] ddvche:
Answering my own question here are the partition names and block sizes,

ls -al /dev/block/platform/msm_sdcc.1/by-name

lrwxrwxrwx root root 2015-10-26 21:18 adsp -> /dev/block/mmcblk0p16

lrwxrwxrwx root root 2015-10-26 21:18 board_info -> /dev/block/mmcblk0p3

lrwxrwxrwx root root 2015-10-26 21:18 boot -> /dev/block/mmcblk0p40

lrwxrwxrwx root root 2015-10-26 21:18 cache -> /dev/block/mmcblk0p42

lrwxrwxrwx root root 2015-10-26 21:18 carrier -> /dev/block/mmcblk0p37

lrwxrwxrwx root root 2015-10-26 21:18 cdma_record -> /dev/block/mmcblk0p33

lrwxrwxrwx root root 2015-10-26 21:18 control -> /dev/block/mmcblk0p30

lrwxrwxrwx root root 2015-10-26 21:18 custdata -> /dev/block/mmcblk0p22

lrwxrwxrwx root root 2015-10-26 21:18 ddr -> /dev/block/mmcblk0p14

lrwxrwxrwx root root 2015-10-26 21:18 debug_config -> /dev/block/mmcblk0p28

lrwxrwxrwx root root 2015-10-26 21:18 devlog -> /dev/block/mmcblk0p38

lrwxrwxrwx root root 2015-10-26 21:18 dsps -> /dev/block/mmcblk0p15

lrwxrwxrwx root root 2015-10-26 21:18 extra -> /dev/block/mmcblk0p32

lrwxrwxrwx root root 2015-10-26 21:18 fataldevlog -> /dev/block/mmcblk0p27

lrwxrwxrwx root root 2015-10-26 21:18 fsc -> /dev/block/mmcblk0p34

lrwxrwxrwx root root 2015-10-26 21:18 fsg -> /dev/block/mmcblk0p19

lrwxrwxrwx root root 2015-10-26 21:18 hboot -> /dev/block/mmcblk0p11

lrwxrwxrwx root root 2015-10-26 21:18 local -> /dev/block/mmcblk0p31

lrwxrwxrwx root root 2015-10-26 21:18 mfg -> /dev/block/mmcblk0p5

lrwxrwxrwx root root 2015-10-26 21:18 misc -> /dev/block/mmcblk0p24

lrwxrwxrwx root root 2015-10-26 21:18 modem_st1 -> /dev/block/mmcblk0p25

lrwxrwxrwx root root 2015-10-26 21:18 modem_st2 -> /dev/block/mmcblk0p26

lrwxrwxrwx root root 2015-10-26 21:18 pdata -> /dev/block/mmcblk0p29

lrwxrwxrwx root root 2015-10-26 21:18 pg1fs -> /dev/block/mmcblk0p2

lrwxrwxrwx root root 2015-10-26 21:18 pg2fs -> /dev/block/mmcblk0p6

lrwxrwxrwx root root 2015-10-26 21:18 radio -> /dev/block/mmcblk0p20

lrwxrwxrwx root root 2015-10-26 21:18 radio_config -> /dev/block/mmcblk0p18

lrwxrwxrwx root root 2015-10-26 21:18 recovery -> /dev/block/mmcblk0p41

lrwxrwxrwx root root 2015-10-26 21:18 reserve -> /dev/block/mmcblk0p39

lrwxrwxrwx root root 2015-10-26 21:18 reserve_1 -> /dev/block/mmcblk0p4

lrwxrwxrwx root root 2015-10-26 21:18 reserve_2 -> /dev/block/mmcblk0p23

lrwxrwxrwx root root 2015-10-26 21:18 rpm -> /dev/block/mmcblk0p8

lrwxrwxrwx root root 2015-10-26 21:18 sbl1 -> /dev/block/mmcblk0p1

lrwxrwxrwx root root 2015-10-26 21:18 sbl1_update -> /dev/block/mmcblk0p7

lrwxrwxrwx root root 2015-10-26 21:18 sdi -> /dev/block/mmcblk0p10

lrwxrwxrwx root root 2015-10-26 21:18 skylink -> /dev/block/mmcblk0p36

lrwxrwxrwx root root 2015-10-26 21:18 sp1 -> /dev/block/mmcblk0p12

lrwxrwxrwx root root 2015-10-26 21:18 ssd -> /dev/block/mmcblk0p35

lrwxrwxrwx root root 2015-10-26 21:18 system -> /dev/block/mmcblk0p43

lrwxrwxrwx root root 2015-10-26 21:18 tool_diag -> /dev/block/mmcblk0p21

lrwxrwxrwx root root 2015-10-26 21:18 tz -> /dev/block/mmcblk0p9

lrwxrwxrwx root root 2015-10-26 21:18 userdata -> /dev/block/mmcblk0p44

lrwxrwxrwx root root 2015-10-26 21:18 wcnss -> /dev/block/mmcblk0p17

lrwxrwxrwx root root 2015-10-26 21:18 wifi -> /dev/block/mmcblk0p13

sizes

cat /proc/partitions

major minor #blocks name

253 0 262144 zram0

179 0 3817472 mmcblk0

179 1 1024 mmcblk0p1

179 2 32768 mmcblk0p2

179 3 16 mmcblk0p3

179 4 15327 mmcblk0p4

179 5 256 mmcblk0p5

179 6 24255 mmcblk0p6

179 7 256 mmcblk0p7

179 8 256 mmcblk0p8

179 9 2048 mmcblk0p9

179 10 32 mmcblk0p10

179 11 4096 mmcblk0p11

179 12 5120 mmcblk0p12

179 13 1024 mmcblk0p13

179 14 32 mmcblk0p14

179 15 1024 mmcblk0p15

259 0 61441 mmcblk0p16

259 1 5120 mmcblk0p17

259 2 8192 mmcblk0p18

259 3 1536 mmcblk0p19

259 4 76801 mmcblk0p20

259 5 4096 mmcblk0p21

259 6 10240 mmcblk0p22

259 7 7167 mmcblk0p23

259 8 1024 mmcblk0p24

259 9 1536 mmcblk0p25

259 10 1536 mmcblk0p26

259 11 20480 mmcblk0p27

259 12 4 mmcblk0p28

259 13 256 mmcblk0p29

259 14 16 mmcblk0p30

259 15 1281 mmcblk0p31

259 16 64 mmcblk0p32

259 17 1024 mmcblk0p33

259 18 1 mmcblk0p34

259 19 8 mmcblk0p35

259 20 256 mmcblk0p36

259 21 25600 mmcblk0p37

259 22 30720 mmcblk0p38

259 23 14498 mmcblk0p39

259 24 16384 mmcblk0p40

259 25 16384 mmcblk0p41

259 26 110592 mmcblk0p42

259 27 2097152 mmcblk0p43

259 28 1179648 mmcblk0p44

179 16 4096 mmcblk0rpmb

match up the gibberish block names and you can sorta make sense of it, it adds up to ~4million blocks, I suppose that accounts for the 4gb we supposedly have