beluga said:
There is a difference between される form of する and -される suffix.
される form of する is a passive form. For example, XXXに検査される which means, being checked by XXX.
勉強される
コピーされる
検討される
-される prefix is a causative passive form. For example, XXXに読まされる which means being forced by XXX to read. This is only applicable to godan verbs (verbs that does not end with いる、える and not irregular verbs like くる and する)
行かされる
泳がされる
書かされる
A more precise analysis would be to say that :
The passive suffix is -(r)are-, which is attached to the stem of verbs.
Ex: たべられる = tabe+(r)are+ru / かかれる = kak+(r)are+ru
Stem+passive+conclusive
In traditional grammar, you say that there are 2 passive suffixes, which both attach to the mizen base in -a of verbs : られる for godan/yodan and れる for ichidan
The causative suffix is -(s)ase-
Ex: たべさせる = tabe+(s)ase+ru / かかせる = kak+(s)ase+ru
Stem+causative+conclusive
In traditional grammar you say that there are 2 causative suffixes, which both attach to the mizen base in -a of verbs : せる for godan/yodan and させる for ichidan
Going back to the causative-passive form, it is in fact for consonant verbs (traditional godan/yodan) -asare- :
よまされる = yom+asare+ru
But this form can further be analyzed as alternate causative -(s)as- + passive -(r)are-
ex: よまされる = yom+(s)as+(r)are+ru Stem+causative2+passive+conclusive
See for example よます, alternate causative form equivalent to よませる
For vowel verbs (ichidan), we clearly have causative+passive combination :
たべさせられる = tabe+(s)ase+(r)are+ru Stem+causative+passive+conclusive